Measure the length of the boards you want to wrap. Fascia comes in ten-foot lengths, but you can have it cut at the home improvement retailer where you buy it for shorter sections. If your fascia board is three inches wide, order six-inch fascia; if it's longer, order eight-inch fascia.
Slide the longer edge of the fascia between the top of the board and the edge of the roof.
Pull the bottom edge of the metal wrap under the fascia board. Most metal wraps have two 90-degree turns, so it looks like a squared "U." Nail the fascia wrap into place by hammering nails through the cover and into the board beneath.