Run a stud finder over the wall and mark the studs with a pencil when the stud finder lights up.
Place the shelf standard, which is the vertical metal bar the shelves sit on, on top of the wall stud. Stick a pencil through the top hole of the standard at the height you wish the standard to be.
Drill pilot holes into the studs that are slightly smaller than the screws included in your shelf kit. Usually a 1/8-inch bit is suitable.
Align the top hole of the metal standard in the Ikea shelf kit with the pilot hole drilled into the wall. Insert the screws from the shelving unit into the metal standard's hole and drive them into the wall with a drill.
Mark the next stud over. Hold a spirit level on top of the first shelf standard and make a mark on the next stud to indicate where the second standard should sit. Drill pilot holes for the second standard and hang.
Hold a spirit level against the shelf standards and straighten them before inserting a screw through the bottom hole of each standard.
Hook a shelf bracket into each standard at the height you want your shelf.
Place the shelf onto the bracket and insert a screw into the bottom of the shelf through the holes in the brackets. The screw secures the shelf in place.