Line the fence up with the seam and move your need to the left or right depending on where you want your stitching and where the seam allowance is. In my example, I have my needle to the right.
If you combine edgestitching and topstitching, you get double stitching. Once you have edgestitched, go back with a #1 foot and sew 1/4″ from the seamline.
This is what it should look like.
On this vest I made, I used doublestitching, topstitching, and edgestitching.