It's Simple.. In the G Suite Admin Console navigate to Gmail advanced settings and search 'early.' If the search doesn't work, here's how to manually get to the settings in the admin console.
The new Gmail User interface is efficient, modern and clean. Our personal favorite for office productivity is the add-on bar on the right. Yay for easy access to our calendar in Gmail.
After you've enabled the new Gmail for your domain or organization, your users can opt in individually from their Gmail settings.
If you change your mind, just click Settings Go back to classic Gmail.