Mark and Level
Installation starts with holding the shelf where you want it to go, and placing light pencil marks at each end of the shelf. Measure in 3 to 4 inches from each mark and make another small mark. If you are also placing a center bracket, measure to the center of the outside shelf marks and mark the center spot. Using a level, draw a straight line at the top of each inner mark. Make the mark long enough to be sure that you can line the top of the brackets up level.
Marking Screw Holes
The next step is to hold the brackets up against the level line that you made in Step 1. Mark the screw holes with a pencil and set the bracket aside. Use a small nail to make a starter hole where you marked the screw holes.
Screw Brackets Into Place
Put the brackets back in place, making sure that they are lined up with the top line and the screw starter holes. Install the screws part way in each hole. Check to be sure the bracket is still lined up and then tighten the screws all the way.