These wings were my first run off, they have ribbon straps and that turned out to not work with a strapless dress unless you enjoy welts in your skin. On my new set of wings I did them strapless with a 9 gauge wire structure. The wire inbetween the wings is a "U" shape so it slips into the back of your dress/shirt/corset/whatever. Depending on the weight of the wings you may only be able to use this method with a corset or something similar. If they're lightweight then it should be fine in the back of a dress. But you also have to plan to have a lowered back line so the wings sit correctly. If your costume does have a high back and sleeves then the strap method would work just fine as well. It does come down to how you planned your outfit. I like the strapless wings myself because of how they move from your back and not your arms. Since if they're attached by a strap around the arms, they move with your arms instead, and that can be unnatural looking (even though wings on people aren't natural to begin with! Ha!)
And for the record, I really need to make some tutorials. I think I've typed this out 4 times now haha!
Let me know if you have further questions!