How do I use it with my CCTV?

Dynamic DNS is a service that provides an 'easy to remember' URL for access to your network. This allows you to view your CCTV using a simple web address like http://mycamera.dyndns.org/, instead of an 'ever changing' IP address.

Many routers feature a Dynamic DNS compatible update client. This is a script which sends the IP address for your network whenever your Internet address changes.

Please see the guide available through DynDNS.com. This guide will help you to get the service up and running quickly.
http://www.dyndns.com/support/kb/dvrs.html

If your Router does not support Dynamic DNS, you could use a PC to do the updates (the PC would need to be on most of the time)

Various update client are available from DynDNS.com

http://www.dyndns.com/support/clients/