There are a few things you need to know in order to turn on the camera on an iPhone while recording a video. First, make sure that your phone is turned off and unplugged from the power outlet. Second, open up the Camera app on your iPhone and tap on the three lines in the top left corner of the screen. Third, select “Turn On Camera.” Once you have selected this option, your phone will start to take pictures and videos with the camera as soon as it is turned on.