It is physically impossible to grow wings from your back. A growth like that would have to start in the womb, if it were even possible - and it's not.
If you are attempting "to grow" "astral wings" then it's really all about shaping your intent to form wings on your spirit/soul/astral self. And that's only possible with belief and intent.
So, if you're trying to grow physical wings, stop. It will Never work. If you mean astral ones, just simply will them to be there, as opposed to "growing" them.