click on a game->click on options->ocarina
there should be a button to download codes->click it
once its done, choose which code(s) you want then click apply.
once you hit apply, ocarina should enable itself automatically.
run the game. enabled cheats should work now.
the best way to test if codes are working is to try one that is noticeable immediately.
for example, I used the allow Classic Controller code for Sonic 4 EP1. the game does not normally allow playing with the Classic Controller so having it work means the code worked.
NOTE:WiiFlow does not allow editing codes so any codes that require specifying something manually will not work right.