You're almost done!
Finish up the dress by sewing the loose ties at the end of the halter together. In order to minimize bulk (who wants a strap that is 6 ties deep?), keep the top and bottom ties of the each strap the same length and stagger the lengths of the ties in the middle to make each strap. Cut the straps to the length you want.
You can fasten the straps with buttons, hooks and eyes or even Velcro.
I took the easy route and sewed the two straps together. To wear it, all I have to do is pull the dress over my head and slip my head through the loop. Then I put on the belt and I'm ready to go.
Good luck! If you're interested in reading about some of my other "projects", check out my blog: http://www.notesfromanerdling.blogspot.com/2013/03/the-incredible-shrinking-face.html