Mark Bracket Locations.

Hold one of the brackets over a stud closest to the end of your shelf, with the top of the bracket aligned with the mark representing the bottom of your shelf.
Make the bracket plumb (perfectly leveled perpendicular to the floor) on the wall by holding a level against the bracket and adjusting it until it’s plumb.
Alternatively, use your level and carpenter’s pencil to mark a long plumb line down the stud’s center mark to hold the bracket against.
Mark the center of the bracket’s screw holes (stamped in the center of the bracket) onto the wall.

Hold the top of a second bracket on the stud at the opposite end of the shelf, and repeat the above steps: holding the bracket plumb and marking the screw holes on the wall.
Heads up: If your shelf isn’t long enough to span two studs, you may need to secure the second bracket to wall anchors instead (see later steps)
Repeat these steps as necessary on any additional brackets you’ll be mounting (i.e. brackets installed in between the two end brackets).
Use a tape measure to center and evenly space these middle brackets.If your shelves require a third bracket in the middle of the two end brackets, divide the distance between the two ends by two to find the center, by 3 for four brackets, etc. For example, for shelves that need a third bracket in the middle with a 48-inch distance between the end brackets, install the middle bracket 24 inches in from either end (48 \ 2 = 24).
You may need to secure these middle brackets to drywall anchors if they don’t fall on a stud once centered.

Are you ready to mount your shelves?