I use cheat codes with USB Loader GX. You should really read the ReadMii that the team have written
but ill tell you anyway. You need to create your own GCT files so you have the cheats you want, I used a code manager by "Link" have a search for it.
You need to create your cheat files and name them under the game code of the game you want to cheat with, For example if i wanted to use cheat codes for Metroid Prime 3, I would need a GCT file called "RM3P01.gct"
Now you have the cheat code file you need to put it on your SD card under SD:/codes
Then go into USB Loader GX, turn on Ocarina from the global settings, then go to in individual game setting for in this example Metroid Prime 3, and make sure ocarina is turn on.
Boot up your game and it will work.
Older revisions of GX would code dump when no cheat file was found so turn off ocarina for the games you dont want to cheat with