Instructions
Purchase a PlayStation 1 game from a local game retailer or online. Most national chains, such as GameStop and Best Buy, do not carry games for the original PS system. However, a local game retailer may have dozens of games for the system. If all else fails, there are several online vendors that you can always order PS1 games from, but their merchandise is typically very expensive, since the games are no longer in production.
Connect the Gameshark CDX accessory to the back of your PlayStation console.
Insert the disc of the game you would like to play. The console will boot to the main menu of the Gameshark.
Navigate through the list of games and locate the one you would like to press.
Press the X button to view all available cheats for the game. Press X again to activate/deactivate any of the cheats.
Exit the Gameshark menu by pressing the triangle button multiple times. The actual game will then boot with the cheat codes you selected.