Draw the piping lines on the wrong side of the fabric. Lay the piping cord down on those lines. Since you are using neoprene, you are going to want to use some sort of clip to hold the fabric together when you fold it over the cord, wrong sides together. Stitch close to the cord on the right side of the fabric.
I recommend you cut your pattern pieces larger to take into account the piping. If I were doing this, I would figure out roughly how much material is going to be taken up by the piping and cut the pattern pieces at least this much wider. Once all the piping was done, I would then cut my fabric pieces to the pattern size.
