Loosen the edge of the shingles next to the edge of the roof -- either by hand or with a pry bar to gently lift the edges of the shingles.
Slide the drip edge underneath the loosened shingles. The outer edge of the drip edge should extend over the gutter – until it is 3/4-inch from the roof. Adjust the drip edge until it is correctly in place.
Drive 1-inch roofing nails into the ends of the drip edge. Be sure to place the nails approximately 2 inches in from the edge of the drip edge.
Apply a continuous bead of roofing cement between the shingle and the drip edge to finish securing it in place. Press down on the shingles to ensure a good seal.