run rhn-register and register.
I know that seems obvious but thats what you need to do. Its a little ncurses wizard and is pretty simple to use.
If you question is "how to install dependencies in a unregisted rhel without registering" the answer is you don't. RHEL charge for their support and that includes accessing their repos.
There are plenty alternatives that offer community based support. If you want to use Red Hat but don't want to or are unable to pay their license fee then I would suggest CentOS which is based on Red Hat but has their proprietary elements removed.
What version of RHEL are you running? 4, 5, 6? In any case, the process is this.
1. Login as root
2. cd to /etc/yum.repos.d
3. Remove red hat specific .repo files.
4. Copy CentOS or Scientific Linux repo files to /etc/yum.repos.d
5. You should be done, except to install/update your packages
I ask what version you are running because I have the repos for CentOS 5 as well as SL6. I can get the repos for you for SL back to version 3, but if your RHEL system is that old, you would be well advised to update pdq.