Even if you don't live in tornado alley, you need to anchor your storage shed to the ground unless it has a concrete foundation. Thunderstorms may produce winds strong enough to damage a shed, along with property around the shed if it gets blown around. Check with your local permit department to see if they, or local building codes, require...
M/F Hammer in a shed anchor at each corner of the shed at a slight angle until the flat cutting surface touches the ground. The anchors head should be a few inches away from the shed's foundation.
M/F Use a crowbar for leverage to twist the tie down into the ground until only the eye loop is showing.
M/F Fish a piece of wire cable, that came with the tie-down kit, under the shed and over the two skids to the opposite side of the shed. The wire will run perpendicular to the skids.
M/F Attach one side of the wire to the shed anchors and secure with fasteners provided. Cut the other end of the wire with a pair of wire cutters, removing as much extra wire as possible. Attach this end to the anchor as before.