Well i managed to get it running but didnt show up right just default unit only.
So here my codes maybe can help me out here. Note: i notced this didnt work if you load up save games, only work when you make a new game.
CIV4ArtDefines_Unit.XML
<UnitArtInfo>
<Type>
ART_DEF_UNIT_RUSSIA_GUNSHIP</Type>
<fScale>0.36</fScale>
<fInterfaceScale>0.7</fInterfaceScale>
<NIF>Art/Units/Gunship/
HIND.nif</NIF>
<KFM>Art/Units/Gunship/GunShip.kfm</KFM>
<SHADERNIF>Art/Units/Gunship/Gunship_FX.nif</SHADERNIF>
<ShadowDef>
<ShadowNIF>Art/Units/01_UnitShadows/GunshipShadow.nif</ShadowNIF>
<ShadowAttachNode>BIP Pelvis</ShadowAttachNode>
<fShadowScale>0.75</fShadowScale>
</ShadowDef>
<iDamageStates>4</iDamageStates>
<fBattleDistance>0.5</fBattleDistance>
<fRangedDeathTime>0.12</fRangedDeathTime>
<bActAsRanged>1</bActAsRanged>
<TrainSound>AS2D_UNIT_BUILD_UNIT</TrainSound>
<AudioRunSounds>
<AudioRunTypeLoop>LOOPSTEP_GUNSHIP</AudioRunTypeLoop>
<AudioRunTypeEnd>ENDSTEP_GUNSHIP</AudioRunTypeEnd>
</AudioRunSounds>
<SelectionSound>AS3D_UN_GUNSHIP_FORT</SelectionSound>
<ActionSound>AS3D_UN_GUNSHIP_FORT</ActionSound>
</UnitArtInfo>
CIV4UnitInfos.XML
<UnitInfo>
<Class>
UNITCLASS_GUNSHIP</Class>
<Type>
UNIT_RUSSIA_GUNSHIP</Type>
....
<Description>
TXT_KEY_UNIT_RUSSIA_GUNSHIP</Description>
<Civilopedia>
TXT_KEY_UNIT_RUSSIA_GUNSHIP_PEDIA</Civilopedia>
Strategy>
TXT_KEY_UNIT_RUSSIA_GUNSHIP_STRATEGY</Strategy>
<UnitMeshGroups>
<iGroupSize>1</iGroupSize>
<fMaxSpeed>1.75</fMaxSpeed>
<iMeleeWaveSize>1</iMeleeWaveSize>
<iRangedWaveSize>1</iRangedWaveSize>
<UnitMeshGroup>
<iRequired>1</iRequired>
<EarlyArtDefineTag>
ART_DEF_UNIT_RUSSIA_GUNSHIP</EarlyArtDefineTag>
</UnitMeshGroup>
</UnitMeshGroups>
<Button>,Art/Interface/Buttons/Units/
HIND.dds</Button>
CIV4CivilzationInfos.XML
<CivilizationInfo>
<Type>CIVILIZATION_RUSSIA</Type>
...
<Units>
<Unit>
<UnitClassType>UNITCLASS_CAVALRY</UnitClassType>
<UnitType>UNIT_RUSSIA_COSSACK</UnitType>
<UnitClassType>UNITCLASS_GUNSHIP</UnitClassType>
<UnitType>UNIT_RUSSIA_GUNSHIP</UnitType>
</Unit>
</Units>
I have checked the path for those .nif and .dds files they are correct and not sure what to do about the .kmf since there was none on customize units that people make for download units. Dunno about _FX.nif either. And one more thing in
CIV4Infos.XMLthat green field, my guess that where you can name your units on the fields, yes? Becuz it say "TXT_KEY_UNIT_RUSSIA_GUNSHIP" in the game when i enter worldbuilder and place it for testing.
At first i had this code, but it crashed becuz of... (Hmm this happen only when i loaded my saved game) it worked when i make a new game but no newer unit, just default unit.

<Units>
<Unit>
<UnitClassType>UNITCLASS_CAVALRY</UnitClassType>
<UnitType>UNIT_RUSSIA_COSSACK</UnitType>
</Unit>
<Unit>
<UnitClassType>UNITCLASS_GUNSHIP</UnitClassType>
<UnitType>UNIT_RUSSIA_GUNSHIP</UnitType>
</Unit>
</Units>
So i dont know where i doing this wrong or what is lefted out. I wanted to play the game and work alittle after saved so that wont happen. Look like i gotta wait til i get all this right before playing.