Hey new member,
To join the usergroup that states your current rank, go to 'Usergroups'. There should be a drop down menu saying 'Join a group' and 'Which group would you like to join?'
Bring down the drop-down menu and select your rank, for example, Driver. Then click 'View Information', then simply click 'Join Group'. It'll send a request to the group leader, in this case Davis Greene and they have to accept you. When they do, you're in!
To Group Leaders: Do exactly the same as what i've said above but you gotta check your group each time you come on. If there are any pending members, see if they're actually in the gang and accept/decline them.