A shot from the rear of the bike, with the seat off, so you can see where the shock is.

This picture is from the left side of the bike.
The preload adjustment is towards the back of the shock.

This picture shows the special tool on the shock preload adjustment ready to adjust.  If your standing in back of the bike facing forward then you will turn it to your right or towards exhaust to tighten the shock preload, be careful the wrench can slip off and it is a knuckle-buster---I found out the hard way.  I did this adjustment after my bike was slammed and it was no big deal at all.

Note: The higher the number, the stiffer the ride (which means the less chance of bottoming out).