Is there a reason you're going below for the wire and not above?

The panel is just held in with clips, that's why he hardly shows it. It's not complicated, just requires some firm pulls. Make sure you get the little light gray piece where the second row seatbelt is removed, that overlaps the quarter panel trim. You can technically remove the panel without that, but it's a little annoying.

 

Is there a reason you're going below for the wire and not above?

Routing it above the AC made more sense and saved me a couple feet of cable, thanks.

 

To remove the inner plastic panel:
Remove the plastic panel in the trunk around the latch. This is held on by two bag hooks. If they spin off without the bolt, use a pair of locking pliers to remove. Apply force to the bottom of the panel and the top to pull out the pins. Peel back the tailgate rubber gasket for additional grip.
Then, remove the bag hook on the passenger side panel. Pull on the back of the panel with the gap behind the door gasket.

You can remove the passenger door kick plate and gasket to get additional grip and remove the entire panel. However, this is not necessary for tucking in the reverse camera wire.

More tips:
Don’t pull from the top of the panel, where it meets the glass. There aren’t any clips here. Instead, pull steadily from the trunk side to pop the rear set of clips, exposing the rear A/C unit. You can then pull more of the panel from there, or use the cupholders.
The panel pulls forward from the upper rear pillar trim, don’t try to separate it in place.

 

Like I mentioned above, you can't forget the C pillar trim where the sliding seatbelt thing is at if you choose to remove the whole panel. The panel can technically be removed without touching that piece, but since it overlaps, it is somewhat of a pain to remove without doing that.

 

The included wire for most reverse camera installations is about 20 feet/6m, which will just barely reach the radio (tailgate --> right harness boot --> rear panel trim --> door kick plates --> blower motor).
I eventually soldered an extension, as the connector snapped due to stress. Never thought about the headliner, however.