Step 1. Go to main screen on your iPhone and open camera application. Swipe towards right to see the video options, You will see the flash button at the top left corner to toggle flash on/off, you can also switch between the front and back camera on your iPhone by tapping on top right corner.
Step 2. To start the recording, hit the “Record” button and once the recording is finished, tap that button again to stop the recording.
Tips: Sometime, you might want to record time lapse videos on iPhone. Here is the detailed tutorial >>