Instructions
Turn on your PlayStation 3.
Navigate to the "PlayStation Network" tab.
Select "PlayStation Store."
Enter your PlayStation Network user name and password into the fields required and select "Login."
Select "Demos" from the menu at the left of the screen.
Select the icon labeled "PS3." All demos available for the PlayStation 3 will be displayed.
Select the demo you wish to download. It will be downloaded and installed to your PlayStation 3 hard drive, where it can be played from the "Games" menu on your PlayStation 3's main menu.