CLICK THE ABOVE BUTTON FOR MORE DETAILS
Android: Go to the device's Settings menu. Select Applications. Select Manage Applications. Select the app. Select Force Stop to close the app. Return to the main screen and relaunch the app
Apple iOS7 & iOS8: Double press the home button to bring up the app switcher. Swipe left or right until you see the app to quit.Touch and hold the app preview and swipe it up off the screen
Apple (all OS versions below iOS7): Double-tap the Home button, then tap and hold the app icon. When it starts jiggling, tap the red circle icon to quit the app. Press the Home button again and tap the app icon to relaunch.