Go to Settings>(More settings>)(Security & Privacy>More security settings)Security>Screen pinning, turn it on;
2. Open the app where you want to pin(lock) the screen;
3. Slide upward from the bottom of the screen to bring up Control Center, then slide the app downward in Control Center, you will see a Pin icon . Touch it to pin(lock) the screen.
You can simultaneously press the Power button and Volume up button to exit Screen pinning.
For Funtouch OS 3.0, you can press and hold the Back button to exit it.
