To edit the Navigation, go to Content > Pages > Navigation
Creating your site's navigation is as simple as creating pages and quickly drag and dropping them to create your Site Map.
Parent (1st Level) navigation items display when the main navigation is expanded.
Child (2nd level) navigation items will display when the parent (1st level) is selected.
3rd Level navigation items will display when the child (2nd level) is selected.
This theme is not designed to show navigation items that are 4th level or beyond.
Video Tutorial: Adding A Navigation Item