Joying radio, no sound on door or oem back camera
 

Just wanted some guidance on what cable to slice to turn on the amp for the door speakers can turn on. I also want to use the oem camera but I'm not sure what i need to do. It shows no signal on screen when I go in reverse. I know it may in a inverter to change the 12v to 6v so it does blow out the camera, I'm just not sure how to do it. It is a joying radio and my car is a 2017 86.