Hi Netra,
2 ways through PFCG role:
1. you need to assign the PFCG role to only 1 approver, so that only he/she can approve
2. PFCG role can be assigned to multiple approvers, needs to be a dummy role, i.e it contains no auth. objects or insufficient auth., to approve the function; AND only the approver who needs to approve can have auth. to approve the function.
Regards
Plaban