Answer:
After all of the confusing layouts...Do you have the sewing directions in front of you? If so, read to where it starts with the SEWING DIRECTIONS and then the fabric key. Costume ABCDE... If you are following costume AB, follow step one. If you are following costume CDE, start at step 2. The interfacing is the ones with the pictures that have the # signs all over them. Make sure you match your dots and such. Otherwise it will come out wrong. You actually stitch the facing to your material. Cut out the interfacing with the same pattern you used to cut out your fabric. Pin, sew. Since I am unaware of which view you are doing, it makes it kinda hard to answer too much more. If you do not have the sewing directions in front of you or have them at all, I would suggest contacting Simplicity directly. Their website is www.simplicity.com.
I am needing help myself on this particular pattern. I was having to rearrange her desires to the correct pattern, etc. Princesses, they are such a pain. Good luck! I hope I helped.