Custom Town Hall

Hey I could use some help.
I made my own version of a town hall, all three stages,a nd I imported it that seemed to work, and I made a custom unit fromt he human town hall and replaced the model file with mine, but how do I get it to upgrade to my second and third version isntead of the orginial humans? and How do I get the peasants to buidl that isntead of the old townhall? ANy help would be great thanks.

well make 2 copies of the building and name in "required animation names" the animation you put for each of the level. e.g stand alternate 1, stand alternate 2.