If you are talking about the round flashing lights that are mounted on top of the fender, they usually have 2 lenses that snap on and off. One for front and one for back. A flat head screwdriver will typically do the trick. Just look for some sort of insert hole at the edge of the lens.
If you are referring to the other rear set of lights, maybe they were modified by a previous owner because the parts diagram just shows 2 screws through the lens, and likely standard automotive type bulbs.