Single Sign-On is enabled by default.
To update this setting, navigate to Manage > Integrations from the web dashboard then scroll down to the authentication methods section. From there you can click to enable or disable Single Sign-On for users on your G Suite.
As long as the domain in their email matches your booking user account (e.g. both are @yourcompany.com) then they will automatically join your company's Robin account. If you need extra Google domains whitelisted for your account, send us a message.