One sec I had a write up on this let me find it
Found it
this is the left rear light if your facing the front of the car
Lift the circled part (it will only lift about 5mm) stick a flat head screw driver in the slot and push the metal clip in (toward the back of the car)
(pretend the red line is the roof)
To sum up, stick a flathead perpendicular to the end of the light. Push the screwdriver inwards, pull the light downwards.