To add more pages go to Edit Page > Add Page. This will give you the option to add a new blank website page, an external page, or default pages like a blog or an online store. From the Edit Pages menu you can also reorder pages to change how they appear in your navigation menu, hide a page from your navigation, and configure SEO settings.
To create subpages (nested pages within your dropdown menu) click the settings button for the page you want to nest. Under "Is a subpage of" select the parent page you want it to appear under. Click Done to save the change and Publish to make it live.
Add Default Pages
To quickly add pages that already contain a few blocks to get you started, you can select from a list of default pages on the Add Page menu. You can add additional blocks to default pages just as you would with blank pages.