The Ratings app has a tabbed interface with two screens. With a storyboard it is really easy to create tabs.
Switch back to Main.storyboard, and drag a Tab Bar Controller from the Object Library into the canvas. You may want to maximize your Xcode window first, because the Tab Bar Controller comes with two view controllers attached and you’ll need some room to maneuver. You can zoom out using the little floating panel in the bottom-right corner of the canvas.