We will firstly need to add the RPMForge public key, so YUM doesn’t wine about the validity of the source:

rpm --import http://dag.wieers.com/rpm/packages/RPM-GPG-KEY.dag.txt

and then install the RPMForge package, that simply adds RPMForge’s sources to YUM:

CentOS 4 x86:

wget http://packages.sw.be/rpmforge-release/rpmforge-release-0.5.2-2.el4.rf.i386.rpm
yum install rpmforge-release-0.5.2-2.el4.rf.i386.rpm

CentOS 4 x64:

wget http://packages.sw.be/rpmforge-release/rpmforge-release-0.5.2-2.el4.rf.x86_64.rpm
yum install rpmforge-release-0.5.2-2.el4.rf.x86_64.rpm

CentOS 5 x86:

wget http://packages.sw.be/rpmforge-release/rpmforge-release-0.5.2-2.el5.rf.i386.rpm
yum install rpmforge-release-0.5.2-2.el5.rf.i386.rpm

CentOS 5 x64:

wget http://packages.sw.be/rpmforge-release/rpmforge-release-0.5.2-2.el5.rf.x86_64.rpm
yum install rpmforge-release-0.5.2-2.el5.rf.x86_64.rpm

CentOS 6 x86:

wget http://packages.sw.be/rpmforge-release/rpmforge-release-0.5.2-2.el6.rf.i686.rpm
yum install rpmforge-release-0.5.2-2.el6.rf.i686.rpm

CentOS6 x64:

wget http://packages.sw.be/rpmforge-release/rpmforge-release-0.5.2-2.el6.rf.x86_64.rpm
yum install rpmforge-release-0.5.2-2.el6.rf.x86_64.rpm

You can now search the RPMForge repository or use:

yum search <packagename>

to search the repository.