Shape Shoulders and Neck: (RS) Bind
off 5 (5, 6, 5) stitches at beginning of next 2 rows, 4 (5, 5, 6)
stitches at beginning of next 4 rows; and at the same time,
on first row of shoulder shaping, work across to center 30 (30,
32, 34) stitches, join second ball of yarn and bind off center
stitches, work to end. Working both sides at the same time, at
each neck edge, bind off 2 stitches twice.
I get all the instructions up to the bolded and underlined parts. I do not understand the rest, about joining the second ball of yarn, etc. Can anyone help me, please?