In order to install apk file to the Android device, basically we need to do the following. 1. On Android device, navigate to 'Apps' > 'Settings' > 'Security', enable 'Unknown Sources', then tap 'OK' to agree to enable this setting. This will allow the installation of third party apps and standalone APKs.

The . apk file is saved on the external storage, but all private user data, databases, optimized . dex files, and extracted native code are saved on the internal device memory.