Point your client to the IRC server chat.freenode.net or irc.wesnoth.org (a DNS pointer to the first) using port 7000 and join…
- #wesnoth: the main channel for user assistance and general support.
- #wesnoth-offtopic: the social and off-topic channel for miscellaneous talk and discussion of subjects not directly related to Wesnoth.
- #wesnoth-dev: the developers’ headquarters and discussion channel, where brainstorming, commenting on new features or patches, and other “important” activities take place.
Free IRC clients include Quassel (cross-platform), HexChat (cross-platform), WeeChat (cross-platform), Irssi (cross-platform), ChatZilla (Firefox add-on), Konversation (Linux), and Colloquy (Apple OS X). Wikipedia also has an extensive list of IRC clients classified by platform support.
If you don’t have an IRC client or your network or ISP does not allow you to connect to IRC, you can also use freenode’s Web gateway service to connect, or try other IRC ports available for connecting to the network.
There are more IRC channels listed on the wiki: see Support/IRC for a complete list of Wesnoth-related IRC channels and servers.