How to install APK files

If you need to install an application outside Google Play for different reasons, you have to learn what is an APK file and how to intall it.
An APK file is an application package created for Android devices ,used to distribuite and to install  Android components.
Now let's see how to install it .
From your Android device you have to go  to Settings , scroll to Security and select Unkown Source.

The next step is to find the .apk  and download it  on your smartphone,tablet ,or computer. In this phase you have to be careful to malware, and download the APK from trusted Web sites .
Finally , you can find the APK file (using a File Manager) ,install it and it's done!
After the end of installation , is  recomended deselect Unkown Source , to avoid
 downloading dangerous applications .