The configuration of the GNOME panel is simple. If you right click on any empty section of the panel a menu will appear. From this menu you will see there are a few options to select:
Add a Panel - This allows you to add an element to the panel. When you click on this a new window will open. This new window allows you to add a pre-configured element (such as the various applets) or create a custom launcher for your panel.
Properties - This will reveal the Properties window of that panel. The Properties window allows you to configure the look and the location of that particular panel.
Delete This Panel - This allows you to delete the panel in question.
New Panel - This allows you to add an empty Panel to your desktop. The empty panel will appear on an empty edge of your screen. You can add anything to this new panel.
Help - This will open the GNOME help application.
About Panels - This will open the About information window, telling you which version of the GNOME panels application is installed on your system.