pop the middle "screw/cap" thing so it's loose (won't fully come out like everyone already said). then get something flat and little wider than a typical flathead screwdriver to push up UNDER the outer circle base. should slide out like a ho.
btw, invest a couple bucks in something like @
Tcoat posted. I have a set of panel trim removal tools and it makes life SO MUCH EASIER in little shit like this.