Note: not all WordPress themes have two or more display locations in the navigation menu. Some might have just one, others might offer up to five or six places to display your menu (e.g., in the Footer, in the sidebar, etc.), but the steps for creating and managing a secondary menu are the same.
Step 1 — Create the Secondary Menu
First, you need to create a new menu. Go to Appearance → Customize → Menus → and click on Create a new menu. Enter the menu name, let’s call it Secondary Menu.
You can assign this menu to the Secondary Menu display location.