The easiest method of doing this is with a keyboard shortcut: Shift+CMD+F (hold Shift and Command, press F). This will toggle you in and out of full screen mode, meaning that if you are browsing regularly, doing this will send the browser full screen and if you are already full screen, pressing these keys will return you to normal.
You can also touch your mouse to the top of the screen, wait for the menu bar to appear, then click View → Exit Full Screen.
The F11 key toggles full screen in Chrome for Windows. Press it to go full screen, and press it again to return to normal. Alternatively, touch your mouse to the top center of the screen and click the Exit Full Screen (F11) message that appears.