Place your .txt codes inside SD:/cheats and make sure they are just a cheat txt with the title id of your game, for instance, story of seasons tot should be SD:/cheats/000400000019F500.txt like that, now inside SD:/luma/plugins have a folder called ActionReplay and have the action replay plugin inside like this SD:/luma/plugins/ActionReplay/ActionReplay.plg and lastly take the boot.firm from the luma 9.0 fork and place it in the root of your sd like SD:/boot.firm
That should do it, go to your game and you should get a green flash
on the top screen it will say plugin loaded at the bottom right corner of the screen, when inside the game, press select and click on action replay, a list of your codes will be there