Back in Gnome 2 there was a very useful user account editing gui tool whereby I could easily add or edit a user to a group. For example, I could give a standard user access to something that they hadn't installed or don't have default access too, such as Me-TV. How do I do this in Gnome 3 / Unity?

I am not allowed to create the tag "edit user accounts" or similar and there isn't anything similar existing, strangely. I'm guessing there is a totally different way to edit user accounts or no one bothers - perhaps no one shares PCs anymore.