USe the nails that glenn recommended and hand nail. You need to remove the entire shingle. This will involve removing old nails up under the good shingles.
Your goal is to not to have any nails show and the new shingle to be nailed in roughly the same place as the old one. You can then use some "black jack" (black roof cement) to seal the front edges of the old shingles down to the new. You will need a flat bar, often called a wonder bar, to get up under the shingles to get the nails out.