Please contact your G Suite administrator to install ContactBook for your Domain.
To install ContactBook for your domain, your G Suite Admin should follow the steps given in the link.
Our application uses Google Contacts APIs. So for the first time, G Suite Admin will have to install the application domain wide and provide necessary permissions to access their Google Contacts on behalf of the organisation.
It is a one-time process. Post installation, organisation users will be able to login and use the application.