Sometimes when you install a new program from the Ubuntu repositories, it doesn't show up on the menu until you log out and log back in. You can easily reload the Gnome panel though by killing the process and restarting it. Simply open a terminal window and enter the following:

Gnome should automatically restart the panel after a few seconds and your new application should now show up in the appropriate place on the menu. If the panel fails to start, you can run it from the terminal with: