Put on work gloves, boots and safety glasses.
Set up your ladder for easy access to your roof.
Carry your roof sheathing up to your roof one board at a time if you need to build up the roof. Bring up the first board and place it over the roof frame in a straight, even formation.
Use your roofing nailer to nail the sheathing to the roof frame. Repeat this process until sheathing covers your entire roof.
Cover the sheathing with your weatherproof roof membrane using your paintbrush. This material assumes a sticky, glue-like form and goes on in a thick layer that hardens to protect sheathing from moisture.
Allow the membrane to set. Read the membrane manufacturer's instructions to gauge how long this process takes.
Collect your flat seam metal roof panels at the bottom of your ladder.
Read the manufacturer's manual for your roof panels. If you received no manual when you purchased the panels, contact the manufacturer to get one.
Bring your flat seam roof panels up to your roof using the ladder. Carry them up one at a time.
Using the instructions provided in the manual, arrange the panels on the roof so the seams lock together to form a single surface.
Use your roofing nailer to affix the flat seam metal roofing to your roof sheathing. Drive nails through the weatherproof membrane into the wood of the sheathing.
Lock panels together across your roof until they cover the entire surface, repeating the instructions provided by the manufacturer's manual.
Apply weatherproof sealant or caulk, as recommended by the metal roof manufacturer, around and between all roofing panels, as an additional source of weather protection.