Pause the game and press Up(2), Down(2), Left, Right, Left, Right, X, Circle. If you entered the code correctly, you will hear a sound. Note: The code may only be enabled once per level.
Beat the game without using any continues on the normal difficulty level. Then, a level select option will appear on the title screen.
Accumulate at least ten hours of game play on any difficulty level, then save the game. Now restart the game to access free play mode.