For those of you who already know how to use IRC, the channel is #themanadrain on EFNet (irc.efnet.net).
Now for the tutorial for those of you who aren't familiar with IRC:
First, you'll need to download mIRC at
http://www.mirc.com/After installing the program, open it. You should get something that looks like this:

If there is no window inside of mIRC as in the screenshot above, then go to File -> Recent Servers -> New Server Window, and it should appear.
Once here, all you need to do is type the following into the text box one at a time, hitting enter after each one:
/server irc.efnet.net [EDIT: this often no longer works, pick an address here
http://www.efnet.org/?module=servers/nick DesiredNickName
/join #themanadrain
Now, we will go about setting your options so that you don't have to go through entering all of those commands each time. First, go to Tools -> Options, and under the first section on the left-hand side ("Connect"), select "Options," and click on the "Perform..." button. In the dialog box that appears, make sure the "Enable perform on connect" box is checked, click "Add," select EFNet, and click "OK." Then, in the box, type "/join #themanadrain" without the quotes. It should look like this:

Return to the base options menu, and now select the "Connect" category. Here, enter your desired nickname and an alternate one in the event that it is taken. Keep in mind that EFNet limits nicknames to nine characters.
Don't be driven away if there aren't any chats going on; they'll usually pop up eventually. Hope to see you in #themanadrain!
In addition, if you ever have a rules question and need an immediate answer, just type /join #mtgrules in the server window. There should usually be at least one or two people available to answer your questions in there.