It's very easy to get there. If you're using Firefox just download plugin called Chatzilla for it. Then click link
irc://mediatraffic.fi.quakenet.org/smcars
It connects you automatically to our channel. If you want to use certain program for it, then I recommend to download HydraIrc or mIrc. They are more complicated to setup thou.
Here's quick guide how to use mIrc:
-> Open mIRC and then go to view -> options.
-> Choose Connect. Put your nickname there and other information if you wish.
-> Choose Connect-Servers next. To there choose Quakenet to IRC Network and IRC Server can be random.
If you wish that mIRC connects you automatically to the SMCars channel, then choose Connect - Options and from there Perform. Tick the "Enable Perform on Connect". To the list below add this command "/j #smcars". Now every time you push the connect button, mIRC automatically connects you to the #smcars