EPEL (Extra Packages for Enterprise Linux) is a third party RPM repository for Red Hat Enterprise Linux and CentOS.

Here are the steps to add the EPEL repository in Red Hat Enterprise Linux and CentOS 5 or 6:

1. Install the EPEL package using the command below.
# rpm -Uvh http://bit.ly/KANG3P

2. Verify the installation using the command below. You should see epel in the output.
#yum repolist

3. Install the Yum priorities package using the command below.
# yum install yum-priorities

4. Edit the file /etc/yum.repos.d/epel.repo and add the line below under the [epel] section.
#priority=10

5. Test your configuration using the command below. You should see a priority protections message in the output.
# yum check-update