Once you have as many beads as you think you'll want strung onto your yarn (you might want to add a few extra, just in case) move the beads down the yarn far enough so you can comfortably cast on the needed number of stitches without involving the beads (unless you want beads in your cast on, which is also a fine choice).
Continue to knit as normal, pushing the beads out of your way down the yarn as you go, until you get to a point where you want to start placing some beads.
