I'm not a CPanel fan, but there are several online and printed how-tos for that control panel:
http://docs.cpanel.net/twiki/bin/vie...on/CpanelDocs/
Configuring basic security can be simple, but it would be worthwhile to study a basic understanding of firewalls and how to establish rules. I use a mixture of hardware firewall devices and server-based firewalls; but noticed some CPanel users utilize this:
http://configserver.com/
Lastly, understanding your VPS Operating System can be accomplished by many online tools, but I cut my teeth on Linux with an older version of this handbook:
Linux Desk Reference
... but get whatever you prefer to use. CentOS is a good distro, but don't have experience configuring it within VPS environments.