There is 1 notch at the top and 2 at the bottom. The front hitch light is the same - but white instead - have a look if you want.
You should be able to press it down with 2 fingers. squeeze the housing with your other hand (LH & RH side) and it pops out.
Or, very carefully, use a flat blade screwdriver to pry at the top and you will see the notch.
When you put in back, make sure it is tight - as I lost mine on the highway somewhere and had to buy a replacement...
Denis & Diane
2010 Sabre 31REDS
Ford F-250 2011
* Happy Campers *