1) Click the Get it on Google Play graphic above. Your phone will download the APK. Start the installation.
2) Android will ask you to grant permission to either the file browser or your web browser to install the app. Grant the permission and it should bounce you back to the installation screen. If not, navigate back to your Download folder after granting the permission to try again.
3) The app should safely install.
This is a temporary installation method until Google clear the app for use in the Play store.