Hi there,
No problem. Even tho I'am trying the make the UI as intuitive as possible, it always needs some knowledge.
There are 2 tabs in the UI, players and groups. In the players tab you can click the small "two people" symbol on the right side of each players button. It then shows all groups and the player can be added or removed from all the groups.
If you want to manage it the other way round, you may go with the groups tab and also click that "two people" symbol on the right of each group. Then it shows all players and you can add or remove them from that group.
In general these small buttons on the right actually do have a clickable purpose. Note that there are different permissions for all available actions, even tho not required if you are server admin anyways.
Hope I could help.
Thanks for using GPerms and Marry Christmas if appropriate.
Best regards
ZockiRR