Regardless of what method you use, you need to adjust some settings on whatever application you use to launch MKWii. There are multiple online and offline tools that will allow you to make GCT files by simply including what cheat codes you want to play with.
The GCT file has a 'header', then the cheat codes, and ends off with a 'final terminator'. A GCT (Gecko Code Type) file is a small file that contains your cheat codes and it resides on your USB or SD device.
