The Download app action allows users to be redirected to any download page. Set the URL of the app to be downloaded, add the App name and Description, and you're all set.
Download app on the App Store
The Download app on the App Store action allows you to redirect users to your app download page on iTunes. It will show the Apple App Store on IOS, and encourage users to download the app. Additionally, you can create a short description which will be displayed above the App Store widget.
Download app on Google Play
The Download app action allows you to redirect users to your app download page on the Google Play stores on Android. This is a great way to get people to download your app.