When inserting the battery, the POWERUP FPV will automatically turn on. The LED lights will flash and eventually set on a constant green light.
When the POWERUP FPV is on, you can use the On/Off button on the back of the airplane to turn it off and back on. However, it is known that with some SD cards the On/Off Button doesn't turn on the airplane.
In this case, take out the battery for turning off and insert it for turning on the airplane.
It's always recommended to take out the battery after flight and keep it separated from the airplane.