SYNOPSIS.
/kick <channel> <nick> <reason>
SUMMARY.
You can only use this command when you are an op (Operator) on a channel. Let's say that you want to kick the user [SQ]werl out of your channel, named #someChannel, you would type.
/kick #someChannel [SQ]werl out!
And you would see on the channel.
[SQ]werl has been kicked from #someChannel by someOp (out!)
Be warned that most users enable the option 'rejoin channel after kick', so if you really want to get rid of a user you will have to ban them first, and then kick them.