If I'm interpreting your question right, you do not add skin as such, but you create a model of what you wish to animate or pose, via nurbs or polys, then you create the joints inside your geometry and bind ( which determines what joints have effects on parts of the geometry) you model and joints together.
Think it best to find some tutorials on rigging if possible to understand further.
Just found this in the free tutorial section here have a look
https://www.simplymaya.com/movie_page...html?tut_id=36
If you believe in telekinesis, raise my right hand.