Now you need to add all the users to the eprocure system.

Whomever you envisage will generate a PO, approve a PO (could be the supervisor, could be the owner, could even be every member of Exco or the Board) and the person in finance who will submit the final PO to the vendor, must all be added to this system. You must also add a vendor administrator as well, even if that person will never generate or approve a PO.