From your android phone, go to Settings, scroll down to Security, and select Unknown sources. Selecting this option will allow you to install apps outside of the play stores. Depending on your device, you can also choose to be warned before installing harmful apps. This can be enabled by selecting the Verify apps option in the Security settings.
Dowload the apk file of the app from the github releases column onto your android phone. Latest version of the app are identified by the highest version number. If you downloaded the APK file on your computer, you must connect your Android device to the PC and enable USB mass-storage mode. Then, drag and drop or copy paste the apk file onto your device.
Locate the downloaded apk file on your phone and click to install the app. The app will be installed with the sheep launcher icon.