Remove any leaves from around the bud you have chosen on the scion.

Beginning just a bit above the bud, cut into the wood and cut down tapering the cut out of the wood and back out through the bark about an inch (3 cm) below the bud.

Peel the bark, with the bud attached away from the sliver of wood you've just removed.  If it does not slip, Stop , and submerge the scion in cool water overnight, retry with a new bud the next day.