If you're a Commvault Cloud customer, access Cloud Rewind via the Commvault Service Catalog, with your Commvault customer credentials. In the Cloud Rewind tile click Manage, or Request Trial if you haven't yet subscribed.
Otherwise, once you've subscribed to Cloud Rewind access the Cloud Rewind portal for your location and log in with your email address and password.
The email ID used to subscribe to Cloud Rewind is the root user. Once logged in as the root user, you can create and manage additional users, roles, and SSO.