When I first bought my pop-up blind, I set it up, zipped up the windows and left it for a month for the deer to get used to it. When we sat in it for the first time, every deer noticed that black hole and the window flaps were down. The next year I set it up and left just the front down 24/7. I even put a few apples right in front of the blind so they would notice. Once deer season came around, not one deer noticed me in the blind.
Another thing I have heard people do is leave a dummy in the blind so that the deer get used to seeing something in the blind. When you arrive to hunt, the deer think they are looking at the dummy.