First, begin a one-player game. Play until you get the option to save the game on the controller pak. After saving, reset the game. Select the load game option from the main menu, then choose the saved game. A prompt to insert a rumble pak will appear. Hold the L+B buttons for approximately a second, then press the A button. A level Selection Screen will appear that allows any mission to be played under the current difficulty setting. Take note that the difficulty setting can be adjusted by entering the Option Screen from the Main Menu.