How To Add Units To Other Factions?

[ratbarf]

Sorry but for the death of me I cannot seem to find an answer to this question. All I want to do is let all the gun powder units be available to all of the factions in the games... As well I would like to be able to give mongol horse riders muskets... Could some one please help me.?

Also I need to know how to add the units to the buildings so they can actually be built in the campaign game by the AI and the current player faction.

Thanks
Ratbarf