Ok, i never used mIRC before, so i don't know [CENSORED] about how it works.
I understand there is a soldat channel. And from what i understand, this is where the action is.
Can someone tell me how to join this?

mIRC is just one of many clients, IRC is the whole idea/protocol/system etc.

Anyway, you just enter your nickname/email etc. in the options and then you connect to QuakeNet (irc.quakenet.org) and join one of the Soldat channels.
You can do all this by typing this:

/server irc.quakenet.org -j soldat.forums

Or just go to http://u13.net/irc/