Push up on each side of the plastic light cover with your fingers to force the tabs in the sides of the cover out of the slots in the light housing.
Grasp the front edge of the cover and pull it straight out of the bottom of the range hood.
Slide the rear tab in a replacement cover into the slot at the rear of the light housing.
Press up on the center of the cover to bend it slightly, and then push the tabs in the sides of the cover into the slots in the sides of the light housing.
Let go of the cover to lock it into place.