Follow the instructions in this post to get your identifiers… Add this to your server.cfg
Then take the second identifier (the one that says license) and replace the <your_licence_goes_here> in the example below with the identifier…including the license: part!
Then take the example below, with your license pasted in, and paste it into your sever.cfg. Change the group to whichever group you want the player added to.
add_principal identifier.license:<your_licence_goes_here> group.god