Work over 17 sts in the pattern, then turn and work back to the end of the row on the WS. Then starting with the RS row, dec a st at the neck edge (where you turned) and on every row for 8 rows. You have 9 sts left and then work them until it's the same length as the armhole on the back.
Leave the rest of the sts on the end of the needle and just ignore them, or put them on a stitch holder. You'll get back to them when this shoulder is finished.