Hi Nasir
there should be a KB article in marketplace or if you search for permission group in GRC space you will find your answer. I think you define as ^! Followed by a name (e.g. ^!relcode) or similar. Search and you will confirm way to maintain. You do this on the action tab and then add the authorisation on permission tab.
the permission group is something you define so you can group the permissions together in lieu of a transaction.