To turn something on, typically a switch. A noun or pronoun can be used between "flick" and "on." As soon as I flicked on the light, I could see that the house had been robbed.
flick something on
to turn something on, using a toggle switch. Mary came into the room and flicked the light on. Please flick on the light.
To activate by switch; switch on: We flicked on the lights and entered the attic. Flick the heat on when you get home.