If you are a BP record owner or creator, you can transfer ownership at any time in the workflow process, other than the creation step, or after its termination step. The new owner will have all privileges of a BP owner, and the originator name on the BP form and the log will show the new owner.
To transfer ownership
Open a BP record. From the Edit menu, click Transfer Ownership. Choose the user from the User/Group picker and click OK. The selected user becomes the BP’s new owner. You can also transfer a record from the BP log, Actions > Transfer Ownership. If you have enabled to view forms in the redesigned user interface, the option to transfer ownership is under 
Menu > Transfer Ownership.