I use Debian, but these package names might get you started:
ddclient - address updating utility for dynamic DNS services
ddns3-client - Issues dynamic DNS v3 requests
ez-ipupdate - client for most dynamic DNS services
inadyn - client to alleviate the requirements for an Internet name
ipcheck - Dyndns.org client to register your dynamic IP address
I'm sure one of those is available on CentOS. All you'll have to do is configure the client with your username and password. Since I use pfSense, I use TSIG:
Let me know if you have any follow up questions once you install a dyndns client.