Asus RS520-X5/PS8 - Manual (Page 24)

Chapter 2: Hardware setup 2-6
2. Twist each of the four screws with
a Philips (cross) screwdriver just
enough to attach the heatsink to
the motherboard. When the four
screws are attached, tighten them
one by one to completely secure
the heatsink.
2.2.2 Installing the CPU heatsink
To install the CPU heatsink:
1. Carefully place the heatsink on top
of the installed CPU.