Need Help With Pattern and Some Scarf Progress

I am sure this is easy but I can't figure it out. I wrote to the pattern writer and she got back to me right away. But then her site went down for my next question and I never heard back so I am posting it here. The pattern is here and below is where I am so far, front and back of body done except for the problem area which is the next of the front piece.


What I don't understand is this line:
Neck: Rib 14 (15, 18) sts, join another strand of yarn, bind off center 29 (31, 31) sts, finish
row. Working both sides at once, work until rib measures 1.25" (1.5", 1.5"). Bind off
14 (15, 18) sts each side.

How do you join another strand of yarn here? Why if you already have yarn? I'm confused. Below is the 14 rib stitches completed. If I add another strand am I knitting with two strands. In other words how am I carrying this strand across the bind off. And how do you work both sides at once?

Here's where I am with the scarf. I'm almost half way through. The cable and lace pattern is much more apparent in real life but I can't seem to convey that in my photo. The shot without the flash shows it off the best but it's still not a great representation.


Update: Got some replies from Ravelry (knitting site) and here is the one that spelled it out because sometimes I just need it spelled out.

If anyone is interested:
OK, using the small size as an example: Using your original skein, rib 14 sts. Then drop that yarn from your hand. Just leave it hanging; don’t cut it or carry it. Take another skein of yarn, & bind off the next 29 sts; you’ll want to leave a tail of about 8 inches or so, which you’ll weave in later (& maybe trim some off, t/b/d). When you finish binding off those sts, continue ribbing the remaining 14 sts using the new skein of yarn (i.e., the skein that you’ve just used to bind off the center sts). When you get to the end of the row, turn as you normally would, & work the pattern (purl, or whatever for a WS row) on those same 14 sts. When you get to the end of those 14 sts, drop that yarn, pick up the yarn from the original skein that’s just hanging there waiting for you, & work the WS on the 14 sts that the original skein is “attached” to. So you’re never carrying any yarn, & never working 2-stranded. Just working each half using its own skein. You’ll just need to take care that the 2 skeins don’t get too tangled! ;P

Thank you knitsnknishes!