How-to Photoshop: How to Combine 2 Images Seamlessly in Photoshop for (Beginners) to (Advance)
Transform/Combine 2 Images Seamlessly, Like you see on the internet! All the time!
Amazing Horse Jumping Off Cliff! Change/Erase Backgrounds-Merge Layers-Place Images 
I teach you how to combine 2 images.
For beginners/Basics, example
Photoshop: Photo-Manipulation (Tutorial)