Pull the first panel up from the eve. Align the center rib of the panel over top of the gable end truss. Do this top and bottom of the panel. Ensure that the eve has roughly 3 inches of overhang on both sides of the panel. Squaring the posts and leveling your trusses properly will make this process very simple with a square building. If your building is out of square you will have to kick the panel or shift it up and down to account for the rise/fall of the sheet metal as you lay each panel.