Hello,
To input a cheat code the player must:
1. enter Free or story mode (free is recommended)
2. (at any point in the game) type the code starting with
"Key Backspace" > "Key Right Shift" > (some letters, corresponding to the code)
In case there's still an issue, feel free to contact me via nymphokyun@gmail.comI hope this helps ;)
~NK