In addition to that helpful link, Its easy enough to open a channel, just type /join #channelnameyouwant. Controlling it is another matter. Check the website of the network you go to (use a search engine like www.google.com
with the name of the network), they should have lots of info on their policies and commands for registering the channel if they allow that and how to manage it. Assuming they have such services, also look into registering your nick, since most will require that as a first step to registering a channel.
The network prolly also has help channels that can walk you thru the steps, they may be listed in the MOTD (Message Of The Day, to read it, type /motd). Some also have commands you can type for info, like /chanserv help
It may all sound confusing at first, but take your time and go step by step. its not so bad honest