How to install unknown Apps? Fix unknown Apps To install apps from unknown sources on an Android device, you can do the following: Open Settings Go to Security or Security and Privacy Tap More Security settings or Special app access Tap Install unknown apps Select the app you want to install from unknown sources Toggle the Allow from this source switch to enable the option You should only activate unknown sources when you trust the source of the app you're installing. Apps downloaded from unknown sources can make your device and personal data vulnerable to threats like ransomware. Google only guarantees that apps from the Google Play Store are safe.