Learn and train how to setup the explained network services without having to browse too much docs. In the practice test you are only allowed to use documentation that is shipped with RHEL.
Also daily work with RHEL is mandatory. For example how to administer user accounts or set file permissions on the system.
An imho interesting part is around troubleshooting a messed up system.
Learn how to use rescue media to fix corrupt RHEL servers.
The outline of the exam is not secret. Get it from
www.redhat.com (or read it in books) and prepare yourself.