Look at the bottom sides of the device indicated by the arrows numbered 1 and 2.

Left side (arrow number 1)

Right side (arrow number 2)

Look at the left side and pull at the end of the back plate in the direction indicated by the arrow (1) in order to detach the backplate.

Then repeat this step for the other side (2)

Once both ends are freed, you can simply pull on the backplate upwards to remove it.