If your overlays are in JPG format, all you have do to use them is to change overlay's layer blending mode. Check what suit's your needs best. You can try different modes. Here are few examples.
- Load you image, add overlay layer,
2. Change it's blending mode to screen
3. Lower opacity, add layer's mask and remove all unneeded parts with the help of soft brush.
Here we'll use normal mode, remove some opacity and use mask.
For layer rotation right click and it and choose horizontal flip.
Change blending mode to overlay.
Buy Light and Shadows. Window overlays and Plant Shadows Overlays