To force stop an application on an iPhone:
- At the home screen, or while in an app, swipe up from the bottom of the screen and pause while still pressing the screen.
Or, if your iPhone is an older model, double-press the Home button.
- When the App Switcher comes up, swipe left and right through the different app cards to find the app that you want to close.
- Use a quick swipe upwards to close the app.