All you have to do is grab your model and import it into Maya and align it with the skeleton as best you can(if you can change the pose to match the skeleton before you export it do that) then match the skeleton with the mesh
Bind the mesh to the skeleton and rig it
Add a skin (low poly mesh for fluids collisions)
Few little extra things but that's about it
I don't know if i will do a tutorial for this because version 4 will be different
but if you do want a tutorial and are interested in adding new models to the game i will
(Don't say yes if you are not going to do it

)