Decide the size and number of holes required. Place the cabinet shelf on the workbench. Use the measuring tape to determine the location of the holes. Place a mark with the pencil to indicate the center of the hole.
Put a drill bit into the electric drill. Tighten the bit in the chuck according to the drill manufacturer's instructions.
Place the shelf on the workbench so that the location of the hole is over the edge of the bench. You do not want to drill a hole into your bench. Firmly push down on the shelf to hold it to the workbench.
Put the tip of the drill bit on the pencil mark representing the center of the hole. Put the drill in the forward position and depress the trigger. Hold the drill straight and press gently as the drill bit enters the shelf. Drill all the way through the shelf. Repeat this process for the rest of the holes. Change drill bit sizes, as necessary.