Hold the hook up to the area of the aluminum patio cover where you plan to install it. Draw pencil markings through the screw holes and onto the aluminum to mark their locations.
Drill holes through your aluminum patio cover, extending through the metal, at each of the pencil markings. Make the holes wide enough for 1/8-inch toggle bolts by using a 3/8-inch drill bit.
Line the hook up with the holes. Clamp a 1/8-inch toggle bolt together and insert it into the hole until you hear it snap open on the other side of the aluminum patio cover. Repeat the toggle bolt installation through each of the screw holes to hold your hook in place.