This article fits all WordPress themes.
Before building your custom menu, you need to create your pages first, then navigate to Appearance > Menus, it is recommended to create your Menu from Pages or Custom Links. Check the video tutorial about how to create a simple WordPress menu:
Tips: don’t forget to pick up the “Primary Menu” option.
Sub-Menu
If you want to create the sub-menu, you could drag the menu item to edit the menu level, check the video tutorial:
For ART, SEA, Air, and Arnold theme, please note that the level-1 menu item cannot be linked a webpage. You could create a “empty” URL for the level-1 menu item by the “Custom Links”, enter # for the URL:
PS: there are 2 sub-menu style options in Arnold version 2, it is possible to visit the URL of the level-1 menu item by the new sub-menu style(2nd sub-menu style)