Start the game and save it (highlight the square in the middle, choose the second option from the bottom on the right, then choose the top option and press B.). Reset, then at the title screen, highlight New Game and press B, Up, Y, A, Left, Up, Down, Right, A, B, Right, X. A sound will confirm correct entry. Press B a number of times corresponding to the desired scenario minus 1 (e.g. 4 times for scenario 5), then press Start to start the game at the chosen scenario.