catalania:To add a panel, right-click on a vacant space on any panel, then choose "New Panel". The new panel is added to the GNOME Desktop. The new panel contains no objects. You can customize the new panel to suit your preferences. To add an object to a panel, so you can switch desktops 1, 2, 3 or 4... Perform the following steps:
Right-click on a vacant space on a panel to open the panel popup menu.
Choose Add to Panel
The Add to Panel dialog opens.
The available panel objects are listed alphabetically.
The one you want to add to your bottom panel is called the "Workspace Switcher Applet".
For more help with using Gnome Panels:
http://linux.about.com/library/gnome/blgnome4.htm