Summarize:

Put the dress on, then bring the straps up to your shoulders. Twist each strap once right below the front of your shoulders. Make the sleeve as wide as you'd like, and then cross the straps in the back. Bring the straps back to the front you should still have one strap on each side of you and then wrap them around your waist so that the straps are in the back again. Tie the straps in a knot or bow behind you. After you've stepped into the dress, pull the straps up to your shoulders as you would for a normal cap sleeve. Form a knot right below your collarbone in each strap. Spread the fabric out over your shoulders to create the sleeve. Cross the straps in the back and then bring them around to your front. Tie the straps in a bow in the front, or bring them around to the back and tie them. With the dress on, pull each strap onto your shoulders. Create a cross with the straps in the back before pulling them back to the front. Wrap the straps around your waist twice completely. Tie a knot or bow in the front or back of the dress. If you feel like your straps are too long to work with, wrap them around your waist however many times it takes to make them into an appropriate length before tying them.
Create a dress with a cap sleeve. Add a knot to your cap sleeve for a more detailed look. Wear your dress with short sleeves to cover your shoulders.