To access it, you will need a client program to log into a server , then join the channel of your choice. Clients Clients are legion, some are a lot better than others. The best thing you can do is use a few and pick the one that suits your needs. As a general rule, the more features a client has, the longer it will take you to learn. Choosing the right server to suit your needs is a matter of deciding what you want to chat about and who you want to chat with.
Most clients come pre-configured with a number of server addresses.
The best thing to do is just try them. Information Resources IRC Servers list is worth a look. While it is not an ordinary public IRC server, the Sydney Morning Herald Internet Relay Chat News , is worth a visit as they have some good speakers on. The View from Oz Australia is poorly served by IRC servers. Australian users do not have easy access to IRC servers world wide.