It is a pretty steep learning curve, but there is a wiki:
https://github.com/UmbraSpaceIndustries/MKS/wiki
In in order to change functionality of a mks module once launched, you need an engineer on EVA, or you can set it to habitation before launch in the VAB. Also in the VAB, the USI animation cost in a part's details shows how many material kits, etc. it will need to inflate. I think you can launch it already inflated if you like.