basically you've got these little "tabs on gears" that need to be pulled up. You have three at the bottom and I believe one on each side. You need a tiny screwdriver to pull them up.
However, when you pull them up, you need to create a pulling tension from the top, otherside the tabs will fall back in place.
Honestly, it took me 10-15 minutes to take that piece out - it's a pain in the ass.
Oh, when yoru'e there, don't play much with the 4C buttons - they are glued to the vent window, and that glue is very weak - mine fell off so I had to use superglue to put it back in place