Do a long-press anywhere on the screen, and after a moment little red circles with minus signs will appear at the top-left corner of each app. You're now in app-closing mode.
To close an app, you can either swipe up so it disappears off the top of the screen, or tap the red circle on it.
To get out of the app switcher, you can select one of the apps by tapping on its thumbnail, or tap elsewhere on the screen to go back to the previous screen.
To close an app, you can either swipe up so it disappears off the top of the screen, or tap the red circle on it.
To get out of the app switcher, you can select one of the apps by tapping on its thumbnail, or tap elsewhere on the screen to go back to the previous screen.