I need help with neck shaping

Ok, here is the instructions:

[color=red]K19, join second strand of yarn and bind of next 15 sts, k to end. Working both sides at once, work until back measures 19 inches from beg and bind off.[/color]

Ok, do I knit 19, join another ball, bind off with the second strand then knit to the end with the second strand, right? Then the next row I would purl with the second ball until I get back to the first strand then purl the rest of the row with the first strand? Then on the the next row, which is knit, knit with the first strand until I reach the second then knit to the end of the row with the second, etc etc.

Thanks to anyone who can clarify so I do it correctly.

You got it. Each side will have it’s own strand.