Creating a Website Mockup in Photoshop is not the easiest thing to do. You first need "Imagination" and then the tools to make that imagination a reality. I have had several students that wonder about the mockup process. There is nothing easy about it but it sure is fun to make them. Here is a video of a mockup that I did for a client. A mock up is a representation of what the website will look like but it is not totally exact. On this particular mockup there will be a lot of sliding going on that you will not be able to see until the website is live.

Creating Folders and Layers in Photoshop

This first thing that you will have to do is create folders and layers in photoshop. 

Here is the video of the mock-up creation that I made.