Spray the outer perimeter of the bed where you plan to install the composite edging with landscaper's spray paint.
Dig a trench along the perimeter using a shovel. The trench should be 6 inches wide. The depth needs to be 3/4 inch less than the height of the edging so that the top of the edging is elevated 3/4 inch above the surface of the ground.
Position the edging around the outside edge of the trench around the bed. The ends of the edging have a half lap joint so that they can overlap. Leave a 1/4-inch gap between the joints on the overlap for expansion.
Hammer a 12-inch stake on the inside or bed-side edge of the edging every 36 inches, measuring from the center of one stake to the center of the next, around the bed using a mallet. The top end of the stake should be approximately 1 inch deeper than the top edge of the edging.
Drive two screws through the inside edge of the stake into the edging to secure the edging in place using a screw gun. Locate the screws at 1 and 1 1/2 inches respectively down from the top end of each stake.
Fill in around the edging using the dirt that you removed from the trench. This is called back-filling. If you plant to mulch the bed, leave enough room for mulch on the bed side of the edging.