To turn on your bike's headlight, first make sure both the battery as well as the LCD display are powered on.
Once they are, simultaneously push the UP ARROW and the MODE button for roughly 1-2 seconds. This will activate both the front headlight as well as the backlight on the LCD display. Time for some night riding!
NOTICE: Riding a bicycle at night is much more dangerous than riding during the day. Ride at night only when necessary. If you choose to ride in poor visibility conditions, first check to ensure you comply with all local laws regarding night riding. Check reflectors/lighting equipment and their mounting hardware before each ride to make sure they are clean, installed properly, functional, visible, and secure. Wear reflective and light-colored clothing, slow down, and use familiar roads with street lighting when possible while riding at night.