If an app freezes on you, the process to restart it is relatively simple:

1. Press the Home Button once to return to the home screen

2. Double-tap the Home Button twice to bring up the list of your most recent apps across the bottom of the screen.

3. Tap and hold your finger on the icon of any of the apps along the bottom of the screen

4. The app icons will start to shake and a minus symbol will appear in their upper left corners.

5. Tap the minus symbol for the app you want to close. If you are successful it will disappear from the list.

6. Press the home button again to return to the normal iPad interface