For this garment, the smocking will be attached to the bottom of the front yoke. In the picture you can see the front yoke, the piping that I will be using, and the smocked piece. I carefully measured and tied off the pleated piece before smocking, but got so excited about smocking that I forgot to take a picture!
Right sides up, and matching the centers, the piping is then pinned to the smocked piece. The piping should fall right above the first row of smocking.
I like to use my 6 groove cording foot since the tiny piping fits just right into one of the grooves! The stitch is lengthened to about a 3.5 to attach the piping, then back to a normal stitch length when the yoke is attached.
I hope that these pictures have helped solve one of the mysteries for you!