Generally, all you need to do is obtain an IRC client for your computer, and then use it to connect to freenode. Once there, you can “/join” the “#dreamhost” channel.
If you have never used IRC (Internet Relay Chat) before, the following links will probably be helpful:
http://en.wikipedia.org/wiki/IRC Wikipedia article on IRC
http://www.irchelp.org/ IRC Help Archive
http://irc://freenode/ Freenode home page
There is a good list of IRC client software in the Wikipedia article. It may seem like a lot to absorb at first, but it is not really that difficult, and there are many channels available for almost any interest on IRC.