The System bar is at the bottom of the screen and it contains quick-launch buttons, for example the Back and Home buttons. You can add up to two extra buttons to this bar to quickly start apps that you often use.
To add a quick-launch button for an app, do the following:
Select the Home button.
Select the Settings app.
In Settings, select System bar.
Under Quick Launch Buttons, select Assign app.
Select an app from the list to assign to a quick-launch button.
Select the Home button.
Your new quick-launch button is added to the System bar.
To remove a quick-launch button, do the following:
Select the Home button.
Select the Settings app.
In Settings, select System bar.
Under Quick Launch Buttons, select and hold the button you want to remove.
In the pop-up box that appears, select OK to remove the quick-launch button.
Select the Home button.
The quick-launch button is removed from the System bar.