To install app on your Android device you need to allow “Unknown sources” apk installs.
1. In your Android device go to Settings
2 In the General Settings go to Security under Personal section.
3 In Security page under the Device administration go to Unknown Sources (Allow installation of apps from unknown sources) and select it.
4 A Pop up box will be warning you about the change, it should be closed by clicking on OK.
5 Pull down the Notification panel from the top of the screen.
6 Tap App-Release.apk and install.