For APK users,
*Few steps to enble APK installs on your Android device.
1. Go to your phone’s Settings screen.
2. In Settings, tap on Security or (for earlier versions of Android) Applications.
3. Under Security (or Applications), go to Unknown sources and check the box or toggle the switch to allow app installs outside of the Google Play store.
4. You will be warned that installing from unknown sources can result in harmful applications being downloaded to your device. Tap OK to proceed.
5. There you go!