Will someone please explain these (outlined in red) instructions? They do not make sense to me
Welcome to the forum!
A neat way to join the shoulders is with 3 needle bind off. Place the right sides or public sides facing each other and work this sturdy bind off.
The left shoulder front and back will be open. Join a new end of yarn and start picking up sts along the left front neck then knit across the center front sts. Pick up along the right front and finall knit across the back sts. Then follow the directions for the pattern on the neck band and under To Make Up to finish the left shoulder and neckband seam.
Here’s a video for picking up sts that may help. Both shoulders are joined in this video whereas you will only have the right shoulder (right as you would wear the sweater) joined. This is so you can knit in rows on your neckband.