looking at guide quick says basically:
- download the ntr cheat file for game(s) you want (the cheat file is a .plg) .
- put it in a folder named whatever the game's title id is (example of folder name would be 0004000000033500 if the cheat was for American version of LoZ OoT).
- make a folder called plugin on root of sd card.
- move the folder containing the cheat file into the plugin folder on sd card.
- load ntr on 3ds and then load the game.
- seems like either select or x+y opens cheat menu in most games.