If you are on OpenVZ you can reinstall the OS via VPSManager and select CentOS 5.x+WHM/cPanel (we recommend at least 1GB RAM VPS)
if you are using Xen you can manually install cPanel+WHM using these commands:
Installing cPanel/WHM
To begin your installation, use the following commands:
- cd /home — Opens the directory 
/home. - wget -N http:httpupdate.cpanel.netlatest — Fetches the latest installation file from the cPanel servers.
 - sh latest — Opens and runs the installation files.
 - usrlocalcpanelcpkeyclt — Activates your license after installation.
 
see fore more details:
