Bulkheads usually come in kits. Lay out the pieces first and follow the directions step by step, and it should only take you four hours or so build. Before you secure all the bolts, make sure the doors close and latch properly. Then seal the base with mortar. Slope the edges to keep your bulkhead watertight and your basement dry.
Adding a yard shed to your backyard not only provides a space for your yard and garden equipment, it gives you a welcomed bonus. With these items stored elsewhere, you will have gained valuable room in your garage for woodworking or other home projects.