At the main menu, hold down Ctrl and while holding it down, type in "potatoe". "M1" will appear in the upper-left corner of the screen -- standing for Mission 1. Use the numbers on your keyboard to change it to M2, M3, M4, etc... After you've selected whichever mission you want, hold down Ctrl and Enter, simultaneously. Keep holding down Ctrl & Enter until the ship-selection screen shows up.
