Ubuntu 13.04, Raring Ringtail has no Graphical User Interface or GUI for changing the User and Group Settings. Therefore default option is either to use ‘sudo usermod’ command from terminal, which is not difficult after a little practice. For all other command options use ‘usermod — help‘ at the terminal. But for those who want to do things as usual, like me, may install GUI from Gnome 2 which works for ‘Unity‘ as well as ‘Mate‘. This is the command from terminal (Control+Alt+T):
sudo apt-get install gnome-system-tools
This will install the good old GUI (we were using for past many years) in ‘System>Administration in Mate. However in Unity we have to use Dash and typing “users-admin” shall call the GUI.
All the best.