yum update

-------------- For RHEL/CentOS 7 --------------

# wget dl.fedoraproject.org/pub/epel/7/x86_64/Packages/e/epel-release-7-11.noarch.rpm

# rpm -ihv epel-release-7-11.noarch.rpm 

-------------- For RHEL/CentOS 6 --------------

# wget http://download.fedoraproject.org/pub/epel/6/x86_64/epel-release-6-8.noarch.rpm

# rpm -ihv epel-release-6-8.noarch.rpm

-------------- For RHEL/CentOS 5 --------------

# wget http://download.fedoraproject.org/pub/epel/5/x86_64/epel-release-5-4.noarch.rpm

# rpm -ihv epel-release-5-4.noarch.rpm