If I remember right, you have to squeeze the lens.
There are tabs that the lens slip into.
I can't remember if they are on the side or top and bottom.
Do a little exploration...gently.
I had to replace a marker light. I'm sure it's the same system.
Good luck and report back with your findings.
2009 Flagstaff 8528 RKSS
2007 Toyota Tundra DC 5.7L V8
Pullrite Superglide 14K
Air Lift 5000
Prodigy Brake Controller
"I've got a mind like a steele.. a......a steele......um.....uh...... what's that thing called again?