Slip something like a thin standard screwdriver in at the hinge point. Gently pry. May need to option off on sides.
Don't feel bad, I tried three times before seeing a video (on a different brand car) that gave me the hint.
I'm not a fan of hidden connections where you need a manual (AFAIK non-existing) just to take most interior and even the tail lights off. What ever happened to the good old visible screws to hold things together?