It doesn't make sense to me

I’m usually a toy knitter so when I got so far on this shirt I was really pleased with myself but then I got near the end. After I’ve cast off it’s saying I need to:

Join row ends of front neck band to row ends at base of neck shaping. With RS facing and using 3.25mm needles pick up and K43 sts down left front neck from shoulder to top of neckband.

Where am i supposed to be getting these stitches from?

You make them by picking up stitches around the neck. Look at the video for picking up on the Tips page. Start at the back of the neck, pretend your sweater is the L needle and ‘knit’ sts down the front and back up to the top.