To lift the front bezel off the iMac, simultaneously:

Use your thumbs to press in the RAM arms and hold the iMac down.

Use your index fingers to pull the small bridge of material on the front bezel toward yourself.

Pull the front bezel up with your index fingers.

Once the small bridge of material has cleared the RAM arms, lift the front bezel by its lower edge just enough to clear the bottom edge of the rear case.