There is no config in SPRO for Personas 3. This is correct. There is no configuration to do. Just install the add-on & service pack, assign the appropriate roles to your user, and it should work.
Have you run the health check in the admin transaction? Are all the lights green?
Also, the add-on delivers roles in PFCG, but they aren't always generated to produce matching profiles. Without those profiles the roles don't work. Check that the profiles exist, and if not, generate them.
Steve.