The Page Tree / Menu Structure can be found on the left side of the editor. The Page Tree represents the hierarchical navigation of pages. In this area you will be able to see and modify pages and sub-pages, among many other options. This is also the area where you can create multiple language versions of your website.
In the following video you will be able to see the creating and editing pages process, but you can find more specific articles about how to create a new page, copy page, rearrange page order, add subpage and delete pages, by clicking on the links.