Instructions
Purchase an external gaming aid, such as GameShark or Codebreaker. The plug-in device has thousands of pre-loaded cheat codes. Download and add and new codes as they become available. These codes are designed by the game developer and are usually the most effective.
Plug the gaming aid into your system's game slot. Select the game from the main menu then select the cheat code using the control pad on the GBA. You can select more than one cheat code at a time.
Remove the gaming aid and plug in the game cartridge. Turn on the game and you should be able to tell right away that the codes are active. You will have the corresponding cheat such as fully completed saved games, infinite life or unlimited ammo.