Does the pattern call for you to knit the sleeves, top down? If so, could it be that the instruction is directing you to do a provisional cast-on so that you can pick-up one side to work the neckline and then later on pick-up the other side to knit your sleeve down?
For the joining of all the pieces -- the front, sleeve, back, sleeve, I usually break the yarn on all the pieces except for the one where I use the working yarn to work my way around the yoke/neck. Leave a 4-6 inch tail that on the other pieces that you can weave in later.
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