Position the ladder on one end of the roof and measure down 1-1/4-inches from the drip edge on the roof. Mark the spot with a pencil. Move to the other side of the house and mark all the way down the fascia with a pencil. Snap a chalk line from one line to the other to account for the slope.
Pre-dill 1/8-inch holes every 16 inches across the fascia board with a power drill. Line up the fascia brackets at each hole and screw them into place with lag screws. Lay out the first piece of gutter and snap an end cap onto the end.
Set the gutter on top of the fascia brackets and rotate it upward until the back edge slips into the fascia hooks. Drill a 3/16-inch hole through the mounting holes in each bracket, and drill a 1-inch machine screw through the hole. Repeat the process for each of the brackets.
Slide a strip miter joint over the end of the first piece of gutter and attach it with gutter screws. Insert four screws through the miter joint and into the gutter. Install the next gutter in the same manner as the first was installed. Continue down the first side of the house. Measure and cut the last gutter of the first side to size using a hack saw.
Slide a downspout outlet over the last piece of gutter, and secure it with gutter screws just like the miter strip joint. Snap an end cap in place over the end of the outlet. Attach the downspout over the hole with gutter screws, and run it down the side of the house to the ground.