Place the first sheet on the rafters and work from your ladder to attach it. Position the sheet in one bottom corner of the roof, overhanging the gable and bottom edge of the roof frame by two inches. Drive one 5/8-inch hex head sheet metal screw with rubber washers through the metal into the rafters, one every 12 inches.
Continue working from the ladder along this bottom row, overlapping each new sheet along the long edge, on top of the one before and screwing them to the rafters. Screw the last sheet in place and cut it off two inches past the edge of the last gable, using a circular saw with a metal blade.
Overlap the next row above by a few inches, on top of your first row. Screw it to the rafters as before. Add sheets, overlapping the long edge to the end of the roof, and cut off the last sheet with the circular saw as you did with the first row.
Add full sheets as far up as you can. Measure and cut enough sheets to length to fill the top row to the peak. Install them in the same way. Install sheets on the opposite face of the roof, working up to the peak using the same technique.
Fit peak trim along the ridge of the roof, overlapping the top of both sides. Screw the trim to the top edges of the metal on both sides of the roof every 10 to 12 inches.