I lined it up a few inches from the edge of the fabric using my cutting ruler and pinned it in place on both sides. (maggiemugginsdesigns.com)
To add straps — pin them in place once you are wearing the top, then remove the top and sew the straps on. (apairandasparediy.com)
These are the waterproof covers that generations ago were elastic around the waist and legs and pulled up over the cloth diaper pinned in place. (believemidwiferyservices.com)