If you see what look like the flat head of a plastic rivet, carefully pry them up, then pull them at least part of the way out. The stem goes into another piece with four fingers that expand to lock them in place. Sliding that "plastic nail" partway out lets the fingers relax so it can be pulled out. To reinstall them, push the black four-fingered plastic piece in with the nail partly installed, then just push the nail in all the way to lock it in place.
Often there's Philips screws holding the panel on, and there's a little cover over the screw's hole. There will be a very tiny hole in that cap to stick a small pick into to pop that cap off.
I don't think this applies here, but sometimes you'll run into what I call "feather fasteners". I think the correct name is "fender plug" or "fender retainer". They look somewhat like a giant plastic nail, but they have multiple barbs all the way around. There's special forked tools to pry those out. I use a side cutter for electrical wire, with a soft touch so I don't accidentally cut them. It's common for the heads to pull through whatever it is they're holding on. Most of the time you can get them out later and reattach them to the panel. These photos show the fastener and one version of the removal tool.
Images (Click to enlarge)
Dec 28, 2020 at 8:42 PM