Roll out roofing felt and staple horizontal rows to the sheathing on your installation wall. Cut the pieces to fit at the end of the wall with a utility knife. Start the first row with the bottom flush with the bottom of the sheathing. Staple the felt in place with one 1-inch staple every 12 inches. Overlap the next row on top of the first, adding each row above with a 3 to 4-inch overlap along the long edge.
Measure the width of the wall and cut 1-by-3 lumber to fit one row along the bottom edge of the sheathing. Nail this strip in place along the bottom edge of the sheathing with 2-inch nails in a pin nail gun. Measure the height of the wall and cut enough siding planks to fill it from the top of the horizontal strip you installed to the bottom face of the roof at the top of the wall, using a miter saw.
Fit the first piece of siding on top of the horizontal strip with its long edge even with the end of the wall. Nail the siding to the sheathing with 2-inch pin nails, one every 10 inches. Fit the next plank, butted up to the first, and nail it in place. Continue adding full width rows to the end of the wall. Measure and cut a piece to fill the area from the edge of the last full piece to the end of the wall. Nail it in place.
Cut two pieces of 1-by-3 lumber the same height as your siding planks for each corner. Cut 1-by-2 lumber to the same length, one piece for each seam between siding planks.
Nail two of the 1-by-3 s together along the long edge to form a corner trim piece. Nail through the first board into the edge of the second, with the edge of the first flush with the face of the second. Fit one of these corner trim pieces to each corner and nail it over the siding with one nail every 8 inches. Fit one piece of 1-by-2 over the seams between the siding planks and nail it in place. Use one nail every 8 inches.