As detailed in Menus, each menu item is linked to a Page Series. In the Page Series area of Evoke you can add as many Page Series' as you need for your App.
Each Page Series is made up of Pages and, again, you can have as many Pages as you need in a Page Series. The Pages in a Page Series are all the pages that will be used in the functional area of the App, as linked to be the menu item. You can create a new page to structure; if a Page is used elsewhere in the App, then you can "Link" Pages, whcih means that any changes are reflected in all the linked pages; or you can import a copy of another Page, if you choose, so that you can modify a copy of an existing Page to create a new Page.
Each Page Series has its own set of defined Data Sources, additional information regarding Data Sources can be found here.