Soon after you get your free website setup, you will want to change the theme or customize the one that is there. You'll want to add your own content to the prebuilt pages. Most of the other important things have already been done for you when you receive your site.
But menus are special because they can be organized very differently based on the website owner's vision or the needs of the company or product. Thankfully, WordPress makes it very easy to customize the menus on the themes. At least the order and naming of each menu tab, or menu item. Things like colors or font or other design-type of cusomizations may or may not be available on your particular theme. You could always customize a lot of those elements using CSS, but we're not going into CSS today.
So the menus on WordPress can be arranged in whatever order you want, simply by clicking and dragging. If you want a menu that has other sub-menus that appear only when you move your mouse over them, then you just click and drag that menu so it is indented in the menu structure. If you want to change the "About us" Page, to "Learn About Us" or simply "About" you just click on the name and edit it. It's that simple.
Go ahead and give it a try, or watch this video and see how it's done.