To install asphalt shingles start by installing underlayment and new flashing on the roof.
How you install roof shingles.
To start installing shingles line up aluminum drip edge flush with the edge of the roof and make a pencil line at the top on each end of the house.
Install the shingles so that each one is overlapping the shingle directly below it which will conceal the nails.
Pull the drip edge down about a half inch from that line to create a gap between the drip edge and the fascia board.
Repeat this on both sides of the roof.
Then begin nailing the shingles to the roof working in rows and starting at the edge of the roof.
Many pros shingle in a vertical line up the roof because it s much faster.
Using the chalk line snap a line between the two marks to get a straight edge.
Every 5 inches make a new mark until you get to the rop of the roof.
Use your chalk and tape measure to mark about 12 inches up on the roof for the first set of shingles.