I would suggest ironing it first. I didn’t when I did the one in my ‘50 and I think it would have been better had I ironed it first. I agree with marking the centers. Having a helper is a good idea. Hang it on the bows (if your car has those), get the seams straight side to side, then do around the rear and front windows then over doors. Keep your eye on the seams, mine wanted to get crooked when I was doing the ends…….Mark