Instructions
Insert the Gameshark disc into your PS2. The main Gameshark menu will appear on screen.
Select "Games" from the list of options and press "X." A list of Games will appear on screen.
Use the directional pad on the controller to scroll through the list of games until you come to the one you would like the cheats for. Press "X" to select it.
Scroll through the list of cheats on screen and press "X" next to the ones you want to enable in the game.
Scroll to "Done" and press "X." You will be prompted to remove the Gameshark disc and insert your game disc.
Insert the game backup you have on writable disc and begin a new game. The cheats will be enabled in the game.