To close apps that are running in the background, follow these steps:
STEP 1: If you have a Home button, double-click the Home button to show your most recently used apps. If you don't have a Home button, swipe up from the bottom of the screen and pause in the middle of the screen until you see your most recently used apps.
STEP 2: Swipe left or right to find the app that you want to close.
STEP 3: Swipe up on the app's preview to close the app.