Activate a stud finder tool and slide it over the desired installation wall. Stop moving the tool when it lights up, which is where a wall stud resides. Place a strip of masking tape vertically on the wall so you can identify the location later. Continue finding studs the length of the shelving you are installing.
Stretch a chalk line across the wall at the desired installation height. Hold a carpenter's level on top of the string until it is level, and then snap it against the wall.
Align a metal L-bracket on the chalk line above a wall stud so the top of one arm points toward you and the metal bend touches the chalk line. Draw a mark inside each screw hole on the wall. Repeat the process on each remaining stud location to mark them.
Wear safety goggles and create a 2-inch-deep hole in each marked location using a drill and 1/4-inch-diameter bit.
Hold a bracket up to the first stud location and align the holes with those in the wall. Insert a 2-inch-long drywall screw through each hole using a power drill. Repeat the process at each remaining stud location to install the brackets.
Position the shelf on top of the brackets and ask another person to hold it steady. Insert 5/8-inch wood screws up through the bottom holes in each bracket using a drill to secure them to the shelving unit.
Install additional shelves above or below the first one, as desired.