I just installed this camera over the weekend (pretty decent for $15). I ended up extending the power cable with some additional wire and tapping into a switched aux power in the center console. I plugged in the video cable to the dedicated port on my pioneer headunit and connected that side of the small red wire to the reverse gear signal of the wiring harness. The other side of the small red wire I tapped into the orange reverse cable in the hatch (ran cables from license thru grommit on right side of hatch). If you can, test wire with multimeter. This setup allows for it to switch to backup camera in reverse as well as at will with headunit camera button (if applicable).
If you just want to have the backup camera turn on with reverse you don't need to connect to the reverse gear signal. I carefully routed my wires with a hanger/electrical tape & just used a simple wire stripper:
I'd recommend soldering if you can, takes a little while longer, but a much stronger connection. Otherwise a lot of ppl use butt connectors.