By default here is no navigation set in WordPress. You have to create and set main navigation. Please Navigate to:
WP Admin -> Appearance -> Menus
Create a new menus with name “Main Menu” if not created yet. Then add recently added pages, under your menu. From the bottom section (Theme Location) select/check the option “Main Navigation”. Then click Save Menu.
Similarly create Top Navigation and from Menu Settings select Header Top Navigation. You may create many other navigations that you can choose to display on any specific/certain page as customized navigation.