Press RUN at the title screen to come to the next screen. There you should press I, I, I, I, II, II, II, II, right, left, right, left, right, left, right, left. You now have 16 continues (instead of 2).
Password Screen
At the title screen, press Run to enter the main menu. In here, press I, II, Right, Left, I, II, Right, Left, I, I, Left, Left, II, II, Right, Right. If done right, the password mode will appear. Press I to enter it.