Instructions
Load the Action Replay CD into the Gamecube console. A screen will load up prompting you when the disc has finished loading. Then it will reveal a menu of available games.
Cycle through the list of available titles until you find the game you want to add codes into. You can only input codes for each game individually and not as a whole group.
Select "New Code" to input the proper code sequence for your cheat. For available codes, search through the CodeJunkies website. This is the official provider and definitive source for Action Replay code content.
Type in a name for your new code when you have finished inputting the proper sequence. Save it and your new code will appear under the list of other preset codes provided for the game.
Select your code to activate it, then load up your game on the top menu of your Action Replay. Switch the Action Replay with the game disc when you are prompted to do so. Play your game to test that your code works properly.