Instructions
Insert the game cartridge that you want to use the Codebreaker cheat device in conjunction with into the game slot on the Codebreaker cartridge.
Insert the Codebreaker cartridge into the game slot on the Game Boy Advance game system.
Turn on the Game Boy Advance system. You will be presented with a page that warns you that the Codebreaker device is not a Nintendo first-party product. After the warning screen, you will be taken to the Codebreaker main menu.
Use the Game Boy Advance's d-pad to scroll down to the game that you inserted into the Codebreaker device. With the game highlighted, press the "A" button to view the codes associated with that game.
Scroll down to the code that you want to activate and press the "A" button to activate the code. Repeat for all of the codes that you want to use.
Press the "Start" button with all of the codes activated to begin playing the game.