The guide you followed is mainly for developers who want to test or implement new features before they are officially published, or for people who want an installation which doesn’t rely on the myopenhab.org servers.
If you’re the “standard” user profile, ie have a local openhab installation linked to a cloud account with myopenhab.org, then use this link: Google Home & openHAB connection How-To, or follow the procedure from the first post of this thread (Official Google Assistant Integration for openHAB)
If you are more a techy guy who wants to contribute and test/implement new features in openhab that are not yet released, then you can follow this guide here : https://github.com/openhab/openhab-google-assistant1