Create a simple montage - using Duplicate Layers and individual Opacity settings.
This is a really simple exercise and it is also reall fun and creative!
1/. Find patio door/window.
2/. Find three subject images to put in the door/window.
3/. Using repeats, place your first image in, in this case two places.
4/. Alll images need to be resized to fit into the frames. Use Edit/Free Transform, to do this.
5/. Using Layers/Opacity reduce the intensity of the image, so that it can be seen as well as the external view.
6/. Do the same with the other two images.

These are the images used, one with the background removed and another image rotation flip horizontal.

The patio door: