I use the walking foot to attach the binding in order to keep all three layers moving together. 

Starting at your first pin (and leaving your 8 inch tail alone) sew directly onto the marked line along your first side. (Make sure to back stitch at the beginning and end of each seam.)

When you come to the the corner sew to within an inch of the end and then take a few back stitches. (Make sure  not to sew your "triangle of excess", you want that to stay loose because you'll use it later.) Pick up the needle and start 1-inch from the corner on the next side.

Repeat this for all sides.

Once you get back to the first side leave a 4-inch gap as pictured below. This gap is where you'll close the loose ends of your binding strip.