Survey the location in which you wish to construct your shelter. It should be in an area where there are no underground utility lines (you can check your county building and zoning codes for this information). The shelter will take up an area approximately equal to the footprint of the shipping/storage container.
Excavate a hole one foot larger in all dimensions than the container except depth, which should be precisely the height of the container. Fill the hole to a depth of 1' with gravel and line the inside with heavy, rubberized tarpaulin or pond lining (available at lumberyards).
Cut a rectangular hole approximately 2' by 2' in the top of the container and save the piece of steel that is removed. This will be the point of entry into the container and the steel square will be used as the door. Cut two more holes, one at each end of the container. These should have the same length and width as the ventilation ducting you purchased because they will be the entry and exit points for fresh air.
Place the container into the hole you excavated, bringing the lining material up and around the top of the container. Backfill the area between the lining and the walls of the hole with one to two feet of gravel, followed by backfill from the excavation so that the ground slopes gently up the the top of the container without quite reaching it.
Bolt a pair of 2-by-4's across the "door" opening just inside its edge, forming "lips" on which the hatch can rest. Nail or screw the top of the ladder to the inside surface of one of the lips so that one can climb down into the interior of the container easily. Bolt the hinges to the hatch, then lay it in place over the hole and bolt the other end of the hinges to the top of the container so that it can be opened and closed. Drill a hole in the end of the hatch farthest from the hinges and fit it with a knotted rope cord so it can be easily pulled open from above.
Put an L-shaped section of ductwork through each of the ventilation holes so that the top of the bottom leg of the L rests against (and is bolted to) the inside roof of the container. Use 2-by-4's and plywood to construct two 4'-tall boxes, about 2' by 2' in footprint to go over top of these. There should be slits in the sides to permit air to enter or exit the boxes, and the total area of these slits should be about equal to the area of the opening of the ductwork. The roof of the boxes should overhang the slits by about a foot on all sides to keep any fallout particles from entering them, and the slits should be tucked up about 6 inches away from the top.
Construct a Kearny Air Pump (KAP) and fit it to the inside end of one of the sections of ductwork that you installed. Bolt the pulley to the roof of the container about 5 feet away from the pump and run the clothesline/cable from the pump to the pulley so that it may be operated by someone standing under the pulley.
Construct a sloped roof out of 2-by-4's and tarpaulin to put over the hatch. This roof should be about 5 feet square and leave just enough room to open the hatch. Layer a few inches of earth over the shelter, building up a small berm (wall) of earth about 6 feet high around the hatch. Keep a square of tarpaulin of sufficient size to cover the hatch and surrounding few feet near the entry point so that you can toss it overhead as you close the hatch. These measures will prevent fallout from entering the shelter through the gaps between the roof and hatch.