By default, WordPress does not automatically add your pages or posts to the navigation/menus of the site.
Menus can be accessed via the Customizer or from the Dashboard (Appearance > Menus).
Create a new menu
Add pages, posts, custom links or categories to your menu
Once added to the ‘Menu Structure’, your menu items can be dragged and dropped to create your desired order. (The Primary menu can accommodate drop list items.) Assign the display location for your menu from the ‘Menu Settings’ check list.