Usually when you want to install an application on your Android smartphone or tablet, you make use of the Google Play Store, official app store. You can also download applications from other sources or download apps on your computer and transfer them to your Android device. Android apps ends with the .apk extension. To install them manually, you must first allow the installation of applications from unknown sources.
To enable this option, go to Settings > Security > Applications.
Enable the "Unknown Sources" option.
Download the APK file or copy it to your Android Device (SD card or phone memory)