How to install android apps
From your smartphone or tablet running Android 4.0 or higher, go to Settings, scroll down to Security, and select Unknown sources. Selecting this option will allow you to install apps outside of the Google Playstore. Depending on your device, you can also choose to be warned before installing harmful apps
Downloading an app
The next step will be finding an Android package file, also known as an APK, which is the way Android apps are distributed and installed. This is where some people usually run into trouble. Never, and I mean ever, use sideloading as a way to pirate applications; doing so will likely result in your Android device getting a virus. You should only download APK files from trusted developers and companies.
You can either download the APK file on your mobile device or on your computer, although the latter is a little more difficult. To get started, download an APK file using either Google Chrome or the stock Android browser. Next, go to your app drawer and click Downloads; here you will find the file you just downloaded. Open the file and install the app.