To create or modify a permission group all you do is go to "Admins" and then Add or edit a permission group.
The thing to note about permission groups is that when editing a user, they are required to have a Panel group(Global group) other than "None" in order to access the panel. We split server and global groups in order to let you have more control over what your admins can and can't access.
Global groups decide if the user can edit, add, view global things on the panel not related to specific servers.
Server groups decide what servers the player has access to do certain things on. The permissions are fully configurable