Roll out the tar paper along the bottom edge of the roof. Cut it to fit your roof if necessary using sharp scissors or a utility knife. Tack the tar paper in place with a hammer tacker with roofing staples. Alternatively, you can use galvanized nails and a hammer or an electric staple gun with roofing staples. Space out the nails and staples along each edge, and scatter some along the interior of the tar paper strip.