Okay, have you bound off stitches for the underarm, or will you put them on a holder? If you BO sts at one place, then the yarn is at the end of them and you can knit over to the other side and BO there. Same thing if you put sts on a holder - put them on after you knit them, knit to the other underarm and those sts. Either way, the yarn is still attached.
At this point there shouldn't be any difference if the stitches after that are the back or front, they'll both be the same. So just begin to knit the instructions for the back. When you're done with that, cut the yarn and knit the front sts. Then it looks like you knit all the sts in the round again for the shoulders.