Please follow below instruction to install 3rd-party APP.

1. Click “Advanced” to enter advanced settings page.

2. Click right & bottom area 3 times(once per second).

3. Then Android main page will appear.

4. Click “Settings” to enter settings page.

5. Check out the option of “Unknown source” in “Security” setting.

6. Click “OK” button and then you'll be able to install 3rd-party APP (APK) from USB flash disk.