two side edges all at once. starting at one of the top corners, sandwich your apron fabric between the layers of seam binding, and then stitch as close as possible to the edge of the seam binding.
stitch all the way down the side, around the rounded corner, across the bottom, around the other rounded corner, and up the other side to the top. while none of this sewing is truly difficult, the rounded corners will provide the most difficulty to someone who is new to sewing. i recommend working around the corners a little at a time; don't try to pin the whole binding in place beforehand. just stitch slowly 