You'll need another end of yarn because you work both shoulders separately. Continue with the shaping at the armhole edges, knit to the center st, drop that yarn, pick up the other yarn end and bind off 1 st, then finish the row with the new yarn, decreasing at the end. Turn and work to the bound off stitch, drop the yarn, pick up the other and work to the end of the row. Turn, do the armhole dec, work to 2 sts before the split, k2tog, drop the yarn, pick up the other, ssk and work to the end, decreasing at the end of the row. Work back on the WS row, and continue making decs at both the beg and end and at the center neck edges.