Asus PS4 - Manual (Page 23)

2-5 ASUS RS500A-E6/PS4
Apply some Thermal Interface Material to the exposed area of the CPU that the
heatsink will be in contact with, ensuring that it is spread in an even thin layer.
Some heatsinks come with pre-applied Thermal Interface Material. If so, skip
this step.
7. Close the load plate (A), then push
the load lever (B) until it snaps into
the retention tab.
A
B