Sorry, it's not possible right now from the app! The way they are hosting their bundle isn't how we intended bundles to be done (we have a separate bundle system). We know this is an issue though so hopefully a future version of the app will address it in some way.
It's not possible to add a game you downloaded from the browser into the app. This is because the app has to track all the game files for managing update, installation and integrity status.
Thanks