Help! first sweater attempt

How-to Questions
1

I have been knitting hats and scarves and dishcloths with short rows, etc, for about four years now… I am just now attempting my first sweater. I am using the boyfriend sweater pattern by scarlet taylor printed in the creative knitting jan 2008.

Because I am new to sweater knitting, I don’t understand this part: SHAPE NECK BACK: k34, [U]join 2nd ball of yarn[/U] and bind off center 50 sts for back neck; knit rem 34 sts.
[B][U]Working both sides at once with separate balls, dec 1 st at each neck edge (every row) twice[/U][/B]
The bold underlined parts.

Where do you join the 2nd ball? How do you work both sides at once?
does she mean, drop the yarn on one side, tie in somewhere (where?) another ball of yarn, and bo stiches. on same needles work each row, when ending drop yarn and go to next set and pick up other side yarn?

I just have trouble visualizing it I guess? thanks for any help!

2

I think you’ve got it.

To join 2nd ball, just drop the yarn you’re working with, and bo the sts with the new ball, then work to end of row. On the next row, when you reach the bo portion and do your decrease, drop the yarn, then pick up the yarn on the other side.