This page is a simple guide to explain the recommended way to install practice codes on your Nintendo Wii.
First of all you're gonna have to install Homebrew on your Wii. Make sure your SD card is formatted to FAT32 and then click this link for a detailed guide on how to get Homebrew on your Wii. Ignore the "So, what's next?" section.
Unpack the archive and place the Nintendont folder with all of its contents in the "apps" folder of your SD card. If there is no "apps" folder create one in the root of your SD card.
Visit the main site and select your game version from the dropdown menu. Then select all the cheats you want to have enabled from the list, choose GCT as file format and hit "Download". The name of the file you downloaded should be "GMSX01.gct" with X being E, P or J depending on the version you selected.
Note: JP 1.0 and JP 1.1 both use the same ID (GMSJ01). To identify if you own JP 1.0 or 1.1 check the back of your disc. It'll read "DOL-GMSJ-0-00" for 1.0 and "DOL-GMSJ-0-01" for 1.1.
Create a "codes" folder in the root of your SD card if there is none and copy the GCT file you just downloaded into that folder.
Open your Homebrew channel and from there launch Nintendont. Select SD and then press B on your Gamecube controller to see the settings. In your settings, make sure that "Cheats" are "On". You can switch it on/off by pressing A on your controller. (See image below)
Press B again to return to the game list and launch your game. And with that you're done already.
This is not a practice code related issue. You have the following options if that happens to you:
Here's a guide on how to install IO58 for use with Nintendont.
Sample folder structure:
This can have multiple reasons:
The Cheat Manager is a homebrew application that allows you to generate GCTs on your Wii. This way you don't have to redownload your cheatfile everytime you want a different combination. However, you're gonna have to use a Wiimote to control the application
You can download the Cheat Manager from WiiBrew. Unzip the archive and copy the contents into the "apps" folder of your SD card.
Using the generator on the main site, select all the codes you want to have available on the cheat manager and choose "Cheat Manager TXT" as file format instead of "GCT" to download a text file formatted for use with the cheat manager. Create a "txtcodes" folder in the root of your SD card if there is none and copy the generated text file into that folder. The name of the text file doesn't matter if you use this application, since the games ID is stored in the textfile.
Launch the cheat manager and grab your Wiimote. Navigate to your textfile using the DPad and select it with "A". On the following screen press "+" to activate and "-" to deactivate a cheat.
After activating your desired codes press "1" to generate the GCT file. The cheatmanager then creates the GCT file in your "codes" folder, overwriting the old one if there's already a GCT with the same name. If you now launch the game with cheats active the new codes will be loaded.
To use the codes with Dolphin choose "Dolphin INI" as file format instead of "GCT" to download the codes formatted for use with Dolphin. Then right click the game in Dolphin and click on "Properties" and on the bottom left corner of the property window click the "Edit configuration" button. Close the property window. Open the text file you downloaded and copy everything following the "[Gecko]" tag below the same tag in the configuration you just opened. If there is no "[Gecko]" tag (it should be the first tag), create one on top of your configuration file. Save and close the configuration file.
Reopen the property window, select the "Gecko-Codes" tab and check all the codes you want to be active. Most (but not all codes) will work with Dolphin. However, Dolphin has a code limit which is reached rather quickly. So if your game crashes right after it starts, you probably have too many codes active simultaneously.