The first step is to install the starter strip, which is generally bought pre-cut according to dimensions of the roof. The basic function of the starter strip to keep water from seeping into the roof. Make sure that you install the starter strip properly otherwise rain water may leak into the roof, effectively damaging the wooden structure.
Start installing the architectural shingles from the lower left corner of the roof. Work your way from left to right, laying rows of shingles and then moving upwards.
Make sure that you mismatch the layups in adjacent rows of shingles. For instance, lay down the first row without resizing any of the shingles; in the second row use shingles of six inches length; in the third row use shingles of twelve inches length and so forth until you reach the full size of a shingle. This practice will help reduce gaps between the shingles, making the roof covering more durable. Use a pair of heavy scissor to resize the architectural shingles.
After you have laid down all the shingles, you need to make sure they stay in place. Simply hammer roofing nails into the shingles. You will have to choose appropriate size of the roofing nails depending on the thickness of the roofing material. There will be a tar strip on each shingle; hammer roofing nails just below that tar strip.