I will show you simple steps to register your Red Hat Linux server with Red Hat Network (RHN).
Below article is only valid for Red Hat 6 and earlier, for Red Hat 7 use the below link
Register RHEL 7 host to RHN using subscription manager (with or without proxy)
Unregister RHEL 7 using Subscription Manager and Remove System Profile
NOTE: This is only possible if you have a valid subscription from Red Hat Linux
Login to your RHEL server and follow the below given steps
# rhn_register
The below screen will pop up. Click on Next
Provide the Red Hat Login subscription username and password provided to you by Red Hat. Give a suitable profile name for your machine. By default your hostname will be taken as profile name
This is the last step. Click on Finish.
To verify the changes you can login to your Red Hat Customer Portal. Under the entitlements section you should see the registered system as shown below
To view the available repositories entitled to your machine
[root@test ~]# yum repolist all
Loaded plugins: rhnplugin, security
repo id repo name status
rhel-debuginfo Red Hat Enterprise Linux 5Server - x86_64 - disabled
rhel-debuginfo-beta Red Hat Enterprise Linux 5Server Beta - x86 disabled
rhel-x86_64-server-5 Red Hat Enterprise Linux v. 5 for 64-bit x enabled: 15,819
Let me know your success and failure.