Observe there are 3 plastic thumbscrews per lamp -- two on top and one at bottom.

Rotate them 1/4 turn (90 degrees) counter-clockwise to unlock.

If they are difficult to turn by hand, a large flat-head screwdriver may also be used.

Once all 3 screws are unlocked, grasp the lamp housing from the rear protrusion, and pull. If you feel a lot of resistance, try wiggling the screws to ensure they have released.