Instructions
Load the Action Replay into the console for which you are adding codes. Power the console on and wait for the Action Replay menu to load.
Navigate through the Action Replay menus as you normally would. This varies from console to console. For example, with the Nintendo DS Action Replay, you can use the directional pad to scroll through menus and press "A" or tap items with the stylus to select them. On the GameCube, you use the thumbstick or directional pad to navigate and press "A" to select things.
Go to the "Action Replay Codes" menu from the main menu. Scroll through the list of games and select your desired game. If the game you want to cheat with is not in the menu, select the "Add New Game" option.
Follow the on-screen prompts and use the virtual keyboard to enter the game's name. Confirm the name of the game and continue to the code screen. If the game you want to cheat with is already in the Action Replay, skip this step.
Select the "Add New Code" option from the list of codes for your game. Use the virtual keyboard to add a brief description of the code. For example, code descriptions may be things like "Infinite Ammo" or "Invincibility." Select "Next" when you are done adding the code description.
Copy the Action Replay cheat code you want to use by typing it into the Action Replay with the virtual keyboard. Confirm that you have typed the code into the system correctly and select "Next" to complete the process.