This simple tutorial is going to show you how to manage users and groups in graphical way using gnome-system-tools in Ubuntu. It is the old gnome 2 Users & Groups management tool which has been dropped since Ubuntu 11.10. Fortunately it still available in Ubuntu Software Center.
To install this Users & Groups management tool, search for and install gnome-system-tools in Ubuntu Software Center.
Once installed, in Unity dash search for and launch users and groups: