The pattern is available on Craftsy, Etsy, or Ravelry.
It's a basic crochet vest or cropped bolero style with instructions for a simple crochet edging or a ribbed edging. Sizes are for small through extra large. Whether you choose the simple edging or the ribbed edging, you'll work a single crochet all around the outside of the sweater, as explained in the pattern.
This diagram shows where to decrease (sc 2 together) at the back of the neck.
The edging is about 2" wide and in the ribbed hdc pattern it is about 2 rows per inch. If you find that the edging is ruffling too much, work the sc a little farther apart, or skip an sc here and there while working the edging. Further instructions are included in the pattern.
The picture below shows the beginning and end of the edging and approximately where to stop. At this point, you sew it together, as explained in the pattern.
When laying out the three buttons for the green vest, I opted to place them a bit lower. They're not "centered" over the front closure of the vest because it looked like they were too high and there was too much of a "tail" to the bottom front and around to the back.