"Authentication credentials for new customers and partners are provided in an email sent from Cloudera to registered support contacts. Existing users can file a non-technical case within the support portal (https://my.cloudera.com) to obtain credentials."
We plan to try HDP, how can I get the credentials again?
You need active Cloudera subscription to access the platform binaries, this including HDP
FYI, Cloudera no longer offers free download of HDP platform for trial purposes, instead you are welcomed to try out the newer version CDP, and you can follow below guide to start: https://docs.cloudera.com/cdp-private-cloud/latest/release-guide/topics/cdpdc-trial-download-informa...
The documentation you quoted is simply saying that if your organization already has a valid Cloudera subscription, you should reach out to the person who has been designated Cloudera's contact person, because that person would have an email message previously sent from Cloudera with the authentication credentials. If that registered support contact does not have the message from Cloudera with the credentials, then they can open a non-technical case to obtain the credentials.
If your organization does not already have a valid Cloudera subscription, then you'll have to begin that process by contacting the Cloudera Sales Team to find out more about subscription options.
If you're just looking to evaluate a data platform, you can currently do so without an existing valid Cloudera subscription by downloading and installing the Trial Version of CDP Private Cloud Base Edition of Cloudera Data Platform