Peel off the four black tamper-evident stickers covering the heat sink mounting screws.

Remove the four T10 screws that secure the heat sink from the backside of the logic board.

During reassembly, tighten these screws one full turn at a time, alternating in a cross pattern. This will gradually increase the clamping pressure evenly across the surface of the CPU. Continue gradually tightening the screws until they're snug and the entire spring plate lays flat against the logic board.