To continue sewing the horizontal seam, repeat step two, working under the legs of the stitches on each side of the work. Every couple of stitches, pull the yarn tight enough so that the tension of the seam matches the look of the knitting. This will help make the seam less visible, though there is a bit of bulk there because the edges of the knitting are underneath the seam.
When you come to the left side of the work, simply weave in the end of the yarn and you're done.
