Start at the bottom, working in 3-foot sections. When the film goes smooth and starts to shrink, move along to adjacent, unshrunk material. Don't go back over an area a second time with more heat. Shrink-wrap tape reinforces welded seams, covers any holes cut by sharp edges, and repairs the few burn holes that are bound to appear. Hinged door frames can be covered in shrink-wrap, or install zipper doors right in the shed's sides and consider adding a vent or two.