How to install an app from an APK file on a typical Android device?
To install an APK file on a standard Android tablet or phone using a process known as “sideloading,” you need to change your security settings: in your device’s Security screen, you’ll need to enable Unknown Sources. If you don’t do this, Android won’t let you install the APK.
Once you’ve done that, the next step is to copy the APK file to your device from your computer. Assuming it’s in the Downloads folder, navigate to it (using your Android device, not your computer) and tap the APK file.
You should now see a dialog box asking whether you want to install the app and detailing the permissions that the app wants to use. Don’t skip that bit: make sure you know exactly what the app wants access to, and don’t install it if you don’t think you can trust it.
Once you’re okay with everything, you can let the installer do its thing, and the app will be installed.