Here's a summary of the changes I made to the XML files:

In Civ4BuildingInfos.xml at the end of the file before </BuildingInfos> (note the s!  Very important), insert:

        <BuildingInfo>
            <BuildingClass>BUILDINGCLASS_MILITARY_ACADEMY</BuildingClass>
            <Type>BUILDING_MILITARY_ACADEMY</Type>
            <SpecialBuildingType>NONE</SpecialBuildingType>
            <Description>TXT_KEY_BUILDING_MILITARY_ACADEMY</Description>
            <Civilopedia>TXT_KEY_BUILDING_MILITARY_ACADEMY_PEDIA</Civilopedia>
            <Strategy>TXT_KEY_BUILDING_MILITARY_ACADEMY_STRATEGY</Strategy>
            <Advisor>ADVISOR_MILITARY</Advisor>
            <ArtDefineTag>ART_DEF_BUILDING_BARRACKS</ArtDefineTag>
            <MovieDefineTag>NONE</MovieDefineTag>
            <HolyCity>NONE</HolyCity>
            <ReligionType>NONE</ReligionType>
            <StateReligion>NONE</StateReligion>
            <PrereqReligion>NONE</PrereqReligion>
            <GlobalReligionCommerce>NONE</GlobalReligionCommerce>
            <VictoryPrereq>NONE</VictoryPrereq>
            <FreeStartEra>NONE</FreeStartEra>
            <MaxStartEra>NONE</MaxStartEra>
            <ObsoleteTech>NONE</ObsoleteTech>
            <PrereqTech>TECH_MILITARY_TRADITION</PrereqTech>
            <TechTypes/>
            <Bonus>NONE</Bonus>
            <PrereqBonuses/>
            <ProductionTraits>
                <ProductionTrait>
                    <ProductionTraitType>TRAIT_AGGRESSIVE</ProductionTraitType>
                    <iProductionTrait>100</iProductionTrait>
                </ProductionTrait>
            </ProductionTraits>
            <PowerBonus>NONE</PowerBonus>
            <FreeBonus>NONE</FreeBonus>
            <iNumFreeBonuses>0</iNumFreeBonuses>
            <FreeBuilding>NONE</FreeBuilding>
            <FreePromotion>NONE</FreePromotion>
            <CivicOption>NONE</CivicOption>
            <GreatPeopleUnitClass>NONE</GreatPeopleUnitClass>
            <iGreatPeopleRateChange>0</iGreatPeopleRateChange>
            <bTeamShare>0</bTeamShare>
            <bWater>0</bWater>
            <bRiver>0</bRiver>
            <bPower>0</bPower>
            <bDirtyPower>0</bDirtyPower>
            <bAreaCleanPower>0</bAreaCleanPower>
            <bDiploVote>0</bDiploVote>
            <bForceTeamVoteEligible>0</bForceTeamVoteEligible>
            <bCapital>0</bCapital>
            <bGovernmentCenter>0</bGovernmentCenter>
            <bGoldenAge>0</bGoldenAge>
            <bMapCentering>0</bMapCentering>
            <bNoUnhappiness>0</bNoUnhappiness>
            <bNoUnhealthyPopulation>0</bNoUnhealthyPopulation>
            <bBuildingOnlyHealthy>0</bBuildingOnlyHealthy>
            <bNeverCapture>0</bNeverCapture>
            <bNukeImmune>0</bNukeImmune>
            <bPrereqReligion>0</bPrereqReligion>
            <bCenterInCity>0</bCenterInCity>
            <iAIWeight>0</iAIWeight>
            <iCost>200</iCost>
            <iHurryCostModifier>0</iHurryCostModifier>
            <iMinAreaSize>-1</iMinAreaSize>
            <iConquestProb>0</iConquestProb>
            <iCitiesPrereq>0</iCitiesPrereq>
            <iTeamsPrereq>0</iTeamsPrereq>
            <iLevelPrereq>0</iLevelPrereq>
            <iMinLatitude>0</iMinLatitude>
            <iMaxLatitude>90</iMaxLatitude>
            <iGreatPeopleRateModifier>0</iGreatPeopleRateModifier>
            <iGlobalGreatPeopleRateModifier>0</iGlobalGreatPeopleRateModifier>
            <iAnarchyModifier>0</iAnarchyModifier>
            <iGlobalHurryModifier>0</iGlobalHurryModifier>
            <iExperience>0</iExperience>
            <iGlobalExperience>0</iGlobalExperience>
            <iFoodKept>0</iFoodKept>
            <iAirlift>0</iAirlift>
            <iAirModifier>0</iAirModifier>
            <iNukeModifier>0</iNukeModifier>
            <iNukeExplosionRand>0</iNukeExplosionRand>
            <iFreeSpecialist>0</iFreeSpecialist>
            <iAreaFreeSpecialist>0</iAreaFreeSpecialist>
            <iGlobalFreeSpecialist>0</iGlobalFreeSpecialist>
            <iMaintenanceModifier>0</iMaintenanceModifier>
            <iWarWearinessModifier>0</iWarWearinessModifier>
            <iGlobalWarWearinessModifier>0</iGlobalWarWearinessModifier>
            <iHealRateChange>0</iHealRateChange>
            <iHealth>0</iHealth>
            <iAreaHealth>0</iAreaHealth>
            <iGlobalHealth>0</iGlobalHealth>
            <iHappiness>0</iHappiness>
            <iAreaHappiness>0</iAreaHappiness>
            <iGlobalHappiness>0</iGlobalHappiness>
            <iStateReligionHappiness>0</iStateReligionHappiness>
            <iWorkerSpeedModifier>0</iWorkerSpeedModifier>
            <iMilitaryProductionModifier>0</iMilitaryProductionModifier>
            <iSpaceProductionModifier>0</iSpaceProductionModifier>
            <iGlobalSpaceProductionModifier>0</iGlobalSpaceProductionModifier>
            <iTradeRoutes>0</iTradeRoutes>
            <iCoastalTradeRoutes>0</iCoastalTradeRoutes>
            <iGlobalTradeRoutes>0</iGlobalTradeRoutes>
            <iTradeRouteModifier>0</iTradeRouteModifier>
            <iGlobalPopulationChange>0</iGlobalPopulationChange>
            <iFreeTechs>0</iFreeTechs>
            <iDefense>0</iDefense>
            <iAllCityDefense>0</iAllCityDefense>
            <iAsset>2</iAsset>
            <iPower>4</iPower>
            <fVisibilityPriority>1.0</fVisibilityPriority>
            <SeaPlotYieldChanges/>
            <GlobalSeaPlotYieldChanges/>
            <YieldChanges/>
            <CommerceChanges/>
            <ObsoleteSafeCommerceChanges/>
            <CommerceChangeDoubleTimes/>
            <CommerceModifiers/>
            <GlobalCommerceModifiers/>
            <SpecialistExtraCommerces/>
            <StateReligionCommerces/>
            <CommerceHappinesses/>
            <ReligionChanges/>
            <SpecialistCounts/>
            <FreeSpecialistCounts/>
            <CommerceFlexibles/>
            <CommerceChangeOriginalOwners/>
            <ConstructSound>AS2D_BUILD_BARRACKS</ConstructSound>
            <BonusHealthChanges/>
            <BonusHappinessChanges/>
            <BonusProductionModifiers/>
            <UnitCombatFreeExperiences/>
            <DomainFreeExperiences>
                <DomainFreeExperience>
                    <DomainType>DOMAIN_LAND</DomainType>
                    <iExperience>2</iExperience>
                </DomainFreeExperience>
            </DomainFreeExperiences>
            <DomainProductionModifiers/>
            <BuildingHappinessChanges/>
            <PrereqBuildingClasses>
                <PrereqBuildingClass>
                    <BuildingClassType>BUILDINGCLASS_BARRACKS</BuildingClassType>
                    <iNumBuildingNeeded>2</iNumBuildingNeeded>
                </PrereqBuildingClass>
            </PrereqBuildingClasses>
            <BuildingClassNeededs/>
            <SpecialistYieldChanges/>
            <BonusYieldModifiers/>
            <Flavors>
                <Flavor>
                    <FlavorType>FLAVOR_MILITARY</FlavorType>
                    <iFlavor>10</iFlavor>
                </Flavor>
            </Flavors>
            <HotKey/>
            <bAltDown>0</bAltDown>
            <bShiftDown>0</bShiftDown>
            <bCtrlDown>0</bCtrlDown>
            <iHotKeyPriority>0</iHotKeyPriority>
        </BuildingInfo>

In Civ4BuildingClassInfos.xml, add the following right before </BuildingClassInfos> (again, note the S):

        <BuildingClassInfo>
            <Type>BUILDINGCLASS_MILITARY_ACADEMY</Type>
            <Description>TXT_KEY_BUILDING_NATIONAL_PARK</Description>
            <iMaxGlobalInstances>-1</iMaxGlobalInstances>
            <iMaxTeamInstances>-1</iMaxTeamInstances>
            <iMaxPlayerInstances>-1</iMaxPlayerInstances>
            <iExtraPlayerInstances>0</iExtraPlayerInstances>
            <bNoLimit>0</bNoLimit>
            <DefaultBuilding>BUILDING_MILITARY_ACADEMY</DefaultBuilding>
            <VictoryThresholds/>
        </BuildingClassInfo>

In Civ4GameTextInfo.xml, add the follow before </Civ4GameText>.  The other language tabs are probably not necessary, but I included them (unchanged from what I originally copy/pasted from) as a placeholder.

    <TEXT>
        <Tag>TXT_KEY_BUILDING_MILITARY_ACADEMY</Tag>
        <English>Military Academy</English>
        <French>
            <Text>Caserne</Text>
            <Gender>Female</Gender>
            <Plural>0</Plural>
        </French>
        <German>
            <Text>Kaserne</Text>
            <Gender>Male</Gender>
            <Plural>0</Plural>
        </German>
        <Italian>
            <Text>Caserma:Caserme</Text>
            <Gender>Female</Gender>
            <Plural>0:1</Plural>
        </Italian>
        <Spanish>
            <Text>Cuartel:Cuarteles</Text>
            <Gender>Male</Gender>
            <Plural>0:1</Plural>
        </Spanish>
    </TEXT>

In Civ4GameText_Strategy.xml, insert the following.  This file is the "Sid's Tips" tooltip when you mouseover a building in the construction selection.  Insert this before </Civ4GameText>

    <TEXT>
        <Tag>TXT_KEY_BUILDING_MILITARY_ACADEMY_STRATEGY</Tag>
        <English>[COLOR_BUILDING_TEXT]Military Academies[COLOR_REVERT] grant experience points to troops built in their cities. Build them in all cities that will produce military units. Three [COLOR_BUILDING_TEXT]Barracks[COLOR_REVERT] are required to build each [COLOR_BUILDING_TEXT]Military Academy[COLOR_REVERT].</English>
        <French>La [COLOR_BUILDING_TEXT]caserne[COLOR_REVERT] donne des points d'exp&#233;rience aux unit&#233;s entra&#238;n&#233;es dans la ville. Construisez-la dans toutes les villes qui produisent des unit&#233;s militaires.</French>
        <German>[COLOR_BUILDING_TEXT]Kasernen[COLOR_REVERT] erh&#246;hen die Erfahrung aller Truppen der jeweiligen Stadt. Bauen Sie Kasernen daher in allen St&#228;dten, in denen Sie Milit&#228;reinheiten ausbilden.</German>
        <Italian>La [COLOR_BUILDING_TEXT]caserma[COLOR_REVERT] concede punti esperienza extra alle unit&#224; sviluppate nella citt&#224;. Costruiscila in tutte le citt&#224; adibite allo sviluppo delle truppe militari.</Italian>
        <Spanish>Los [COLOR_BUILDING_TEXT]Cuarteles[COLOR_REVERT] dan puntos de experiencia a las tropas que se construyan en las ciudades donde se encuentren. Conviene construirlos en todas las ciudades que vayan a producir unidades militares.</Spanish>
    </TEXT>

For the civilopedia entry, add this to Civ4GameText_Civilopedia_BuildingsProjects.xml before <Civ4GameText>

    <TEXT>
        <Tag>TXT_KEY_BUILDING_MILITARY_ACADEMY_PEDIA</Tag>
        <English>[TAB]Warfare has been a recurring phenomenon throughout the history of mankind, and it continues to plague the world today. Although war is not a desirable situation, it is important that even the most peaceful of societies be prepared for the possibility of war. When warring nations are closely matched in technology and manpower, the army with the best training usually wins battles.Military schools and academies exist all over the world, established for the purpose of training military personnel in the latest methods, tactics, and technology. Men and women who graduate from such facilities possess higher than average command and military and technological skills, making them more effective in combat situations.</English>
        <French>[TAB]La guerre est un ph&#233;nom&#232;ne r&#233;current dans l'histoire de l'humanit&#233; et elle continue &#224; affecter le monde aujourd'hui encore. Si la guerre n'est pas souhaitable, il est important que m&#234;me les soci&#233;t&#233;s les plus pacifistes soient pr&#233;par&#233;es &#224; son &#233;ventualit&#233;. Lorsque des nations en guerre ont &#224; peu pr&#232;s la m&#234;me puissance technologique et le m&#234;me nombre d'hommes, l'arm&#233;e la plus entra&#238;n&#233;e est g&#233;n&#233;ralement victorieuse. Des &#233;coles et acad&#233;mies militaires existent dans le monde entier ; elles ont &#233;t&#233; cr&#233;&#233;es afin d'assurer l'entra&#238;nement du personnel militaire aux m&#233;thodes, tactiques et technologies les plus r&#233;centes. Les hommes et femmes dipl&#244;m&#233;s de ces &#233;tablissements disposent g&#233;n&#233;ralement de capacit&#233;s de commandement et de comp&#233;tences militaires et technologiques sup&#233;rieures &#224; la moyenne, les rendant plus efficaces au combat.</French>
        <German>[TAB]Kriegerische Auseinandersetzungen hat es im Verlauf der menschlichen Geschichte bis zur Gegenwart gegeben. Wenngleich sich niemand einen Krieg w&#252;nscht, ist es dennoch wichtig, dass selbst die friedfertigsten V&#246;lker auf einen m&#246;glichen Kriegsausbruch vorbereitet sind. Wenn zwei Krieg f&#252;hrende Nationen &#252;ber das gleiche technologische und milit&#228;rische Potenzial verf&#252;gen, so ist f&#252;r den Ausgang einzelner Gefechte in der Regel ausschlaggebend, wer die besser ausgebildeten Streitkr&#228;fte aufzuweisen hat. Milit&#228;rschulen und -akademien, die milit&#228;risches Personal in den modernsten Milit&#228;rtaktiken und -technologien unterweisen, existieren in allen L&#228;ndern der Welt. Die Absolventen besitzen nicht nur &#252;berdurchschnittliches Fachwissen, sondern verf&#252;gen auch &#252;ber weit reichende milit&#228;rische und technologische Fertigkeiten, die ihnen in Gefechtssituationen zugute kommen.</German>
        <Italian>[TAB]Le guerre sono un fenomeno che ha interessato e continua a interessare la storia dell'uomo; &#232; quindi importante che anche le societ&#224; pi&#249; pacifiche siano preparate a questo evento. Nel caso in cui due nazioni nemiche si trovino ad avere un livello tecnologico simile, &#232; la preparazione dei soldati a fare la differenza. Le scuole e le accademie militari sono diffuse in tutto il mondo e hanno lo scopo di preparare le reclute agli equipaggiamenti e alle tecniche pi&#249; avanzate. Coloro che si diplomano in questi luoghi possiedono abilit&#224; militari e cognizioni tattiche di alto livello, che li rendono pi&#249; efficaci in situazioni di combattimento. </Italian>
        <Spanish>[TAB]La guerra ha sido un fen&#243;meno recurrente a lo largo de la historia de la humanidad y sigue atorment&#225;ndola en la actualidad. Aunque no es una situaci&#243;n deseable, es importante que hasta las m&#225;s pac&#237;ficas sociedades est&#233;n preparadas para la posibilidad de que se produzca un conflicto as&#237;. Cuando las naciones en guerra se encuentran igualadas en tecnolog&#237;a y mano de obra, el ej&#233;rcito mejor entrenado es el que suele ganar las batallas. Las escuelas y academias militares existen en todos los lugares del mundo, creadas con el prop&#243;sito de entrenar al personal en los m&#233;todos, t&#225;cticas y tecnolog&#237;as m&#225;s modernos. Los hombres y mujeres que se grad&#250;an en estas instituciones poseen habilidades de mando, tecnol&#243;gicas y militares por encima de lo normal, lo que les proporciona mayor efectividad en combate.</Spanish>
    </TEXT>

And there ya go, one new building added to the game.