The first time you access AR Designer, you will see the Create New screen. This is where you choose the type of experience you want to create. You will select from a set of templates in the sidebar area.
As you move your mouse over each option, an illustration describing the experience of that template will appear. Selecting Start on a template will bring you into the editor.
See the article about AR Designer templates for an explanation of mobile augmented reality types, and for a description of each template type.