Hopefully I can be of some assistance. I recently had mine off for an install I was doing.
To get to the clips I believe you are referring too, just pop the lift gate glass and you will see two black round circles just under the latch in the center (we will call them pop clips). To release these push the latch in until it catches and put a screwdriver or narrow putty knife behind one of the black pop clips. Now, push the center of that plug in (smaller circle in center of plug). I used needle nosed pliers to do that. Using your screwdriver, now push the plug out from behind the plastic. They should pop right out. Repeat the process on the other side.
Don't forget, you must also remove the screws in the handle and pull down strap. I am sure you already did that, but I just thought I would remind you. When you do get everything undone to get the back piece off make sure you lift towards the top of the vehicle (towards the rear window), and then pull away.
Hope that helped! Good luck with your install!!