Work your way around the monitor, putting the flathead screwdriver into the space between the front and back covers, and prying up.

Twisting the screwdriver can help, but you can easily mess up the plastic without getting anything out of it by doing so. Be cautious.

Ideally you want to pry at the locations that have the little gaps, which are locking mechanisms.

You should hear a poping sound and the back cover should lift a little if you are prying at the right locations.