Welcome Mamie/ Mrrudd!
Those directions are indeed confusing. It would help if we had a visual idea of what it's supposed to look like. I'm trying to understand what they mean by "back." Please let us know what the front and back look like. Is this a standard sweater with a V-neck front, and a back that goes all the way up to the neck as usual? Or is it some kind of tank top that has a sloping V in the back too? ...I just want to make sure we give you the right instructions.
I can tell you this, though: they do want you to work with two balls of yarn at once. Usually you just knit with one yarn, two rows until you're back to the other yarn, then start using that one for two rows, etc., alternating between them. This is because you'll be working similar instructions for both yarns, so it's less thinking in the end. It could also be worked with just one ball, on only one side until it's complete, then join yarn and do the other side. But it's common to work both sides at once.
KnittingHelp Queen Bee
"There is a vitality, a life force, an energy, a quickening that is translated through you into action, and because there is only one of you in all of time, this expression is unique. And if you block it, it will never exist through any other medium and it will be lost. The world will not have it. It is not your business to determine how good it is nor how valuable nor how it compares with other expressions. It is your business to keep it yours clearly and directly, to keep the channel open. You do not even have to believe in yourself or your work. You have to keep yourself open and aware to the urges that motivate you. Keep the channel open."
— Martha Graham