what u need to do is get a hub for this wheel , prefferably a trailer hub, but not a stepped one.
Then remove the bearings and find a peice of metal bar that fits into the hub.
Then either put a keyway into the axil (the metal rod) and put a matching keyway into the hub. Or drill a hole thought the hub and axil so u can use a bolt to secure it.
lastly find a pully that will fit over the axil and put a keyway in the axil (the pully will have one built in).