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
"Don't ask yourself what the world needs. Ask yourself what makes you come alive and then go do that. Because what the world needs is people who have come alive." Howard Thurman