@slinki:
"Adding" the forged alliance game is not enough, you need to enter your gamekey from your original game into steam.
Then you own a steam version of the game and you can download it as normal steam game.
Thats why the client says you don't own the game at the moment.
@masterchief1327:
i am sorry but i only maintain the mod (error fixing and patching for the latest game version)
So there will be no new units for this mod.
If you want orbital factories and spaceships the use the orbital wars mod:
http://forums.faforever.com/viewtopic.php?f=41&t=12416