The "Edit Users and Groups" option is a shortcut into the GNOME system utilites' user management system.  In order to run the tool, you must have administrator privileges.  Administrator privileges on a UNIX-like system are only provided through the user "root".  Therefore, upon selecting "Edit Users and Groups", you must enter root's password.  When you are finished, click "OK", and you can continue into the GNOME system utilities' user management system.  Please refer to that manual for further information on managing users and groups.  To exit the password request, click "Cancel".
