The backlight is super easy to control. Press the UP or DOWN buttons until you reach the brightness level you like. If you want to turn off the backlight, press the Backlight On/Off button. The backlight On/Off is different than the switch. If you turn off just the backlight, the computer will still recognize a monitor is there, you just wont be able to see the graphics since there's no backlight. If you turn off the switch the entire monitor is off, and it wont be recognized by the computer!
When the backlight or monitor is turned off and an on, it will revert to the same brightness you had before.