We have only used that type of binding twice, and it's been a while. I do remember that we started by opening the binding and sewing into the fold. I don't remember exactly how we did the corners, but they must not have been too hard, because we were able to get it done. Maybe try basting it onto your quilt and playing with it before you sew it down for real.
Ok I went and found a YouTube video that shows how to do it. It's just like regular binding.
https://m.youtube.com/watch?v=aPakMj6XPUY