Help with figuring out how to wear this dress

[Tamzzyn]

This dress is beautiful on (not so much on the mannequin due to lack of curves) but I can't figure out how the sash works. It is sewn into the seam on both sides of the zipper but one side it is sewn on the inside and the other side on the outside. Is it supposed to just drape down the back or an I supposed to do something with it?

Also, when would you date this? 50s or 60s?

Thanks

 

[Circa Vintage Clothing]

Lovely frock! Early '60s I think. Try tying the sashes over each other, in a loose tie over the zipper, like you were starting to tie a bow but just let them hang down.