The heat sink is held down by two plates. The right plate, covering the CPU, has 4 screws. The left plate covering 4 smaller chips, has 2 screws.

To unscrew the right plate, carefully pull up warranty label to expose screw. remove 4 screws.

To unscrew left plate, remove two screws. Carefully detach black cloth tape from heat sink, leaving it attached to the left cooling fan.