This is what it should look like with the elastic pinned, right side out, to the boxers, right side in.
Make sure to check that your elastic is far enough down from the top of the boxer fabric that you can sew it to the fabric without catching in the edge of the elastic. This will make turning the elastic to the outside easier and look more professional.
On my machine, stitch number 6 is the lighning zigzag stitch. This is much similar to the zigzag stitch, except the stitches are broken into sections to allow for greater stretching. It is purported to be more sturdy when sewing elastic for waistbands and other applications requiring the elastic to have more give.
(Continued on next entry due to photo limitations)