1. To see recently used apps, double-click the Home button.
   
2. Swipe left or right to find the app you want to use.
   
3. Select the App to open.
   
4. To close an app, Swipe up. To close all apps, Swipe up on all open apps.
   Note: Learn more from Apple support articles: Understand multitasking and background activity on your iPhone and Force an app to close in iOS.