Short answer: Add a skin modifier to the character model and add all the bones of the biped. Then you'll have to edit the envelopes of the individual bones until everything deforms correctly.
Long Answer: I don't really have time to write a tutorial maybe try this one: [Link to www.3dprevis.com]
Moderator
Long Answer: I don't really have time to write a tutorial maybe try this one:
[Link to www.3dprevis.com]