This video demonstrates how to install a heat sink into a computer.
Make sure you have all components: heatsink and thermal paste.
Step 1: Make sure you have the proper set up for the specific motherboard you are using. Check to make sure that the support brackets are bolted to the heatsink.
Step 2: Apply a small amount of thermal paste and slide it into place.
Step 3: Secure with the bracket on the back side of the motherboard. Install the screws that were supplied with the heatsink. Tighten, but do not put too much strain on the motherboard and chip.
Step 4: Plug in the heatsink fan to the motherboard.