We have double hung windows and full screens on the outside. Is that what you're meaning, how to install the screens on the outside while YOU are inside?

If so, all I do is slide the bottom window up as far as it will go. Take the screen and put it on an angle and lift it thru the window, the top goes out first, it just barely fits but it does because of the angle. Then put the top of the screen into the little groove at the top and then pull the bottom towards you and put it on the bottom. Ours have little silver things that jam into the side grooves and hold the screens in place. They move in and out. They are great finger holds.

Does that help at all?

Ours are similar, except that they have hangers at the top. While you stand inside, you get the screen outside (as described above), then you tilt it so the bottom is about 1-2 feet away from the window, with the top angled back toward the top of the window so you can get the square loops on the screen over the tabs that stick up from the frame. Once you've achieved that, you just pull the bottom of the screen toward you and hook the hook. We generally add a bit of wire, for extra security--once had a cat unhook the hook and end up outside on the roof.

Yes, I think you both have helped. Thanks. I don't know what type of hangers/securing tabs mine have since I haven't taken them out of the box yet (wonder if there are directions in there? lol). I thought I might have to tilt the windows in or even remove one... so this sounds a lot easier!

I'll try putting them in tomorrow if I get a chance. Hopefully they won't end up 15 feet down on the ground. :-)