1) First, navigate to the page where the menus are, this example is the homepage.
Ensure you are signed in as your website's administrator as you cannot access these options as a normal user.
Find the Customize button at the top of the page and click it. This will reload the page.
2) Once clicked a new menu will appear on the left with the website next to the new menu that appeared.
On this menu find the "menu" tab and click it to then get all the options of what menu bars to edit.
3) Once clicked you can select the menus that you wish to edit and in this casethe options are quick links (at the bottom of the page) and Global nav which is the menu that appears on all pages at the top.
Once you click either of these options you will be taken to a new portion of the menu on the left with all of the menu's content.
4) As you can see in the screenshot below you can now see all the categories and their sub pages. Here you can re-arrange them by dragging them around which will then move them in that menu.
Moving the Sub pages will change their order in the drop down but to change the order in which they appear on the menu bar you must move the main categories up or down by dragging.
5) If you wish to add a new option to a menu you can scroll down to the bottom of the page and select add item which will then allow you to add and edit a menu option.
There are other options below also such as when the menu you are editing appears and whether or not to delete the menu.
Once you are finished click publish at the top of the page. You can use the site displayed to the right of the menu to preview changes.