Installing on Android

On your Android phone, open family-forest.com/get in a browser.
Tap to download the app (an .apk file).
Open the downloaded file. Android may ask you to allow installing from your browser — allow it once.
Install, then open Family Forest and sign in.

The app is family-only and isn't on the Play Store — that's why you install it from the Get-the-app page rather than searching for it.