You'll need to use a client. For windows, http://www.mirc.com is the most popular. For other OS's, I have no idea.
If you're using mIRC, fire it up and fill in your info.
Click ok
In the status window, type /server irc.gamesurge.net
Once connected, type /join #reddit
There is also a java version here: http://gamesurge.net/chat/
Once connected, type /join #reddit