GCP's path uses a service account with the Monitoring Viewer role, following the same least-privilege pattern as the AWS and Azure integrations.
In IAM & Admin, create a dedicated service account and grant it the predefined Monitoring Viewer role, which allows reading metrics without any write access to project resources.
Create a JSON key for the service account; this is what Linivo uses to authenticate to the Cloud Monitoring API, and should be handled like any other credential, not committed to a shared repo.
Upload the service account key and select which projects to monitor; Compute Engine instances, Cloud SQL and load balancers appear as devices alongside your other infrastructure.