Position a ladder in an even area of ground next to the roof of the home. Ask another person to hold the ladder steady while you climb up onto the roof carrying a tarp.
Walk carefully over to the area of the skylight and kneel down next to it. Unroll the tarp to the width of the skylight plus an additional 4 feet so it overlaps it. Carry the top edge of the tarp up to the peak of the roof and hang it over the top edge by at least 2 feet. This prevents rain water from hitting the top of the roof and draining down into the tarp. The bottom of the tarp should reach the roof eaves.
Cut a 2-by-4-inch board using a hand saw so it is 2 feet longer than the width of the skylight. Insert the board under the top edge of the tarp and roll the board under it until the tarp wraps securely around the board. Insert roofing nails into the board every 4 to 5 inches with a hammer to secure the tarp to the board.
Place another identical 2-by-4-inch board on top of the tarp-covered one and insert 3 1/4-inch long nails through the board every 6 inches using a hammer so the nails penetrate the roof.
Insert two more boards at the base of the tarp in the same manner to hold it down below the skylight. Secure the tarp to the fascia or the eaves.
Place additional 2-by-4-inch boards along the sides of the tarp and nail them into place using 3 1/4-inch nails and a hammer to hold both sides down.