Here's how you can shut down malfunctioning apps on your iPad, iPhone or iPod. 1. Double push the Home button. 2. The app switcher will appear at the bottom of the screen. 3. Tap and hold the icon of the app you want to close. 4. Tap the red minus in the upper left corner of the icon. The app will be closed and you can relaunch it if you want.
For more, see the original article at the link below.
How to Force-Close a Running iPhone or iPad App | How to Geek