The Certificate of Proficiency (Postgraduate) is not a formal qualification. You should only apply for this certificate if you are intending on only completing one or two postgraduate courses. For example, these may be interest courses or you may want to study them to prepare you for studying another qualification in the future.
See the regulations for more information.
You will need to meet the entry requirements for the courses you choose.
For information on prior learning, exemptions and transfer of credit or other questions: