When I have a picture open and I open another picture, why does it not automatically put them in layers? I have 2 open pictures and have no idea how to combine them. I'm used to Elements 7 where this is so easy and now I have the new 2015 PS version and am LOST.
Because each document you open is a separate document, not layers in a single document. That isn't any different in Elements or the full Photoshop.
If you want to combine multiple documents as layers, you can drag the layers from one document into another, or use the Load Files Into Stack script to merge multiple files as layers into a single document.