Select mesh > Modify Panel > Physique modifier
With bones you use the skin modifier
With biped you use the physique modifier
Click on > Attach to Node (COM)
Pick the COM (from list) this will be listed as Bip 01 then press initialise.
If the mesh pulls you need to go the sub-object level of physique to envelope.
When you see the envelope:
Red envelope means that the skin is competely attached
Maroon means that the skin is semi-attached.
Go to envelope options to Radial Scale to alter the envelopes.