STEP 4: APPLY SKIN MODIFIER
1). Open the Layer Manager and Unfreeze the mesh. Select it in the Viewport. Un-transparent the mesh by hitting [Alt]+[x].
2) In the Modify Panel open the Modifier List rolldown to apply the Skin Modifier If your head and body are separate meshes, apply Skin to each.
3) In the Skin parameters choose the Add Bones button and load all bones. Be careful to not add non-bones, like separate head/body meshes, eyes, etc. In the Layer Manager set the "biped" layer to "hide" so the bones are no longer visible.
Scrub the time slider to see the animated mesh, and initial skinning!
If the location of any joint is off (elbows or knees are too low or high, the shoulders bend too far out, etc), scrub back to frame 0, select the mesh(es), delete the Skin modifier, hit "unlink" in the toolbar, and redo relevant parts from Steps
and : re-transparent and freeze the mesh, unhide and adjust the bones in Figure Mode, unfreeze and un-transparent the mesh, re-apply Skin, turn off Figure Mode and hide the bones to test the animation.
The better you get at the initial bone rig set up (the width of each bone), the better this initial skinning will appear to grab the correct area of the mesh for each bone, but always expect that every skinning will need to have all capsule envelopes adjusted at least a little.