Next I cut off the bottom in two segments. The first cut was to make it the right length for my little girl (which I determined by trying it on her and eye-balling it). Then I cut the bottom 2" off of this in order to make a ruffle border for the bottom on the dress.
Since the circumference of this "loop" of fabric is longer than the circumference of the bottom on the dress, I used my sewing machine to put a long stitch through it and gather it up in order to make it fit the bottom of the dress. This is not a particularly full ruffle since it was not dramatically longer than the bottom of the dress.
Once I did this, I could have just sewed the shoulder seams back together, but I decided instead to cut some strips out of the sleeves I cut off in the beginning and use those to make ties for the shoulders. This makes the shoulders adjustable, and makes for cute little bows! I had to gather the top of the arms pieces a little bit to make it fit the ties evenly since I didn't measure anything when I cut the strips and they were pretty narrow. You can see this in the picture. I kind of liked the effect. Now all that is left is putting the dress on your little girl. My daughter really likes it and hasn't wanted to take it off!