cd /etc/yum.repos.d
wget http://download.openvz.org/openvz.repo
rpm --import  http://download.openvz.org/RPM-GPG-Key-OpenVZ
yum install ovz-kernel-PAE

Now remember to set /etc/sysctl.conf to "net.ipv4.ip_forward = 1"

You can apply the change immediately by running sysctl -w net.ipv4.ip_forward = 1 but remember that you still have to set sysctl.conf

sysctl -p will load and apply any changes to sysctl.conf as well