You'll be attaching the pressure-treated 2-by-4s across the width of the concrete every 16 inches as deck sleepers to support the composite decking. Measure the width of the concrete with a tape measure, and then cut the boards to length using a table saw.
Drill holes large enough to fit a hammer drive anchor through the 2-by-4s with an electric drill. Space the holes 16 inches apart and stagger them down the board's length.
Place the boards into position on the concrete and use the holes as a guide to drill holes the diameter of the anchor sleeves into the concrete. Use a hammer drill equipped with a carbide masonry bit to drill the concrete holes 2 ½ inches deep. Clear the holes in the concrete of dust using either a shop-vac or a nylon brush.
Attach the boards to the concrete using the hammer drive anchor. Push the anchor through each drilled hole and drive the head of the anchor into place to expand the flange of the bolt and hold the board in position.
Place the composite decking boards over the installed sleepers positioned parallel to the side of the house. Leave a gap of 1/8 inch between the first row of boards and the wall of your home, and the same sized gap between each board you place.
Attach the boards to the sleepers using composite decking screws that match the boards in color. Predrill the screw holes, two per sleeper, and screw the boards securely into place using an electric screwdriver to drive the screws flush with the decking surface.