Instructions
Download and install the program GCNCrypt. The program is available for free on Codemasters Project and Gamefront.
Open Dolphin. The program will open to your collection of games.
Right-click on the game to which you want to add a cheat code. A small list of options will appear.
Click "Edit patch file: [GAMEID].ini." The Game's ID will be displayed in the "[GAMEID]" brackets. If this is your first time creating a cheat for the game, click "Agree" on the window that appears to create the file that allows you to use Action Replay codes.
Open GCNcrypt. The program should open with a single input window.
Type the Action Replay code you would like to use and click "Decrypt." The decrypted version of the game will be shown on the right-side of the screen.
Type the decrypted Action Replay code into editable patch file from Step 4, except put a plus sign at the beginning of the code. This will activate it.
Give the cheat a name and click "Save." The cheat will be ready for use the next time you start the game.