This is the default Wordpress tab for creating and managing the location of the menus on your website.
Assign the main menuOnce you are in the menus tab, you will see a Manage Locations tab as well. This is the default Wordpress place to set up your menus for all possible locations.
Split Header Menu
Split header uses two menus at the same time, which means you have to create two menus and assign one of them as a "Primary Menu" and the second one as a "Secondary Menu" in Display Location section
Action Bar & Footer Menu
You can replace the existing social icons menu that appear in the action bar & footer of your website with any other menu you want. You will find this in the manage locations tab, under the name Social Menu Top and Bottom
Custom Menu per page
You can set other menu on each page, it's really easy - while editing the page just select it from a dropdown menu, more about page options here.