When we got our blackout material, we picked out a brand new roll, and my wife said, "we are making a movie screen out of this, SO please no folds!". Besides the slightly odd look, they said "ok, sounds like a cool idea". And rolled our few yards up on a empty tube. When we got it home, we noticed a few wrinkles. We hoped they would go away, and they did once the tension was applied by stapling and pulling the fabric tight. Our fabric was a 55" wide bolt, I would imagine after pulling, its closer to 56"-57".
If its real bad wrinkles, I suppose you could try hanging it up in a humid eviroment for a week, or try low heat ironing. With a iron, I would worry about the vinyl side melting, and since its so thick, I not sure how long you would be there ironing. But you may be suprised how much of a stretch you will get out of it, and how easy those wrinkles disapear under tension, we were!