The Header Navigation Menu is the menu that sits in your header. This menu can have multi-level drop-down menus.
It is best practice to limit the number of top-tier items in your header, to perhaps, no more than 6 items in total. Therefore, if your header has, let's say, a Call-To-Action button and a Hamburger menu (two items), then your Header Navigation Menu should only have four top-tier page links. This is only best practice, though it is great advice to ensure that your header items sit nicely within your header. It also ensures that you focus your website towards the priority items, those that are impactful to your business goals.
HOW TO PUT THE HEADER NAVIGATION MENU INTO THE HEADER?
You can put the Header Navigation Menu in the header as follows: