There are two feet/legs that fold out from the back. These are attached inside the unit, so fold them out before proceeding. You won't be able to remove the back panel if they're folded in.

There is a door on the right side that pushes in to allow access to the SD card port. This is a perfect place to insert your finger to get a good hold on the back panel. Use a finger to pull straight away from the unit to lift off the rear panel. It may stick a little but it will pull right off easily.