To start, open your site in the Websites console. Find the page you'd like to change and select it. You can find Move in the controls at the top, or by right-clicking on the page.
For example, here's how we could change the name of the FAQ page.
In the dialog box that appears, you'll see a 'Rename To' field, where you can change the page name. This will in turn change the last portion of the URL.
Notice that CQ will find and make any necessary adjustments to the pages that are connected to this one in any way. Visit the links on the right to learn more about the Move function, as well as how to properly name pages.