Entering new license number for Norton Ghost

I had a trial version of Norton Ghost that expired.  It is still installed on my computer.  I acquired a valid license from a friend/client.  But I need to find out how to enter the license number.  A screen providing that opportunity does not come up when I try to run a backup (when Ghost asks me if I would like to run missed backups).  Norton Support suggested that I try the community since they no longer support Ghost.  Any help would be appreciated.