Hi,
Go to your WordPress dashboard and navigate to Appearance > Menus.
Select the menu you want to edit or create a new menu by clicking on the Create a new menu link.
Drag and drop the menu items you want to include in the mobile menu.
The mobile menu is created and assigned in Appearance > Menu > Select menu and assigned as “Mobile menu”. This menu will be automatically displayed by the Mobile Menu element of the Header Builder.
https://xtemos.com/docs-topic/adding-menu-to-the-site/
Best Regards.