Tap the wall lightly with a hammer to locate the studs. The wall makes a solid sound when a stud is behind it and a hollow sound in the areas between studs.
Position the first bracket against the wall, over the stud. Mark the screw holes for the bracket onto the wall with a pencil.
Drill a ¼-inch starter hole through the wall and into the stud at each pencil mark. Replace the bracket on the wall and screw it in place, using the starter holes. The wall arm sits below the support arm, so the bracket resembles an upside-down L when installed properly.
Place the second shelf bracket against the wall, placing it over a stud. Set a carpenter's level on top the two brackets and adjust the location of the second bracket until it is level with the first. Mark and drill the starter holes before screwing the second bracket in place.
Set the metal shelf on top the wall brackets, centering it in place. Position the shelf so the lip at the end of the brackets holds it in place.