Setup Navigation Menu -

Navigate to WordPress Dashboard > Appearance > Menus
You can see a panel where you can create a new menu, click create a new menu link to create one.
Give the new menu a name, for example, Primary Menu, then click the Create Menu button to create it.
From the drop-downs on the left, choose the content to add to your menu.
Nest & position menu items by dragging & dropping them.
Be sure to check the box to set the menu as “Primary Menu” from the Display location option.
Save menu

Arnica Ghost Theme