Vendor on boarding process roles - not able to approve/ reject the vendor

Hi All,

I am working on Vendor On Boarding process.

Please can anyone can give me information about roles to be assigned to the user to approve the vendor request after Request is submitted through portal.

As of now for rights Vendor, Vendor Portal Administrator, Vendor Prospect and Administrator are given but user can only see View History option.

Where i need to set the roles ? I tried putting in User roles. In workflows Assignment to users.

Please i need the solution ASAP.

Thanks in advance,