Asus M4A78T-E - Manual (Page 26)

2-6 Chapter 2: Hardware information
Chapter 2
3. Position the CPU above the socket such that
the CPU corner with the gold triangle matches
the socket corner with a small triangle.
4. Carefully insert the CPU into the socket until it
fits in place.
5. When the CPU is in place, push down the
socket lever to secure the CPU. The lever
clicks on the side tab to indicate that it is
locked.
Gold triangle
Small triangle
6. Apply several drops of thermal paste 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 paste. If so, skip this step.
To prevent contaminating the paste, DO NOT spread the paste with your finger.
The Thermal Interface Material is
toxic and inedible. DO NOT eat it. If
it gets into your eyes or touches your
skin, wash it off immediately, and seek
professional medical help.