After selecting a channel; we will use the fictitious #xyz_abc channel as an example; you may see nothing for half a minute or so, depending on what server you have chosen. If your connection is refused, keep trying as the server could just be very busy. If that does not work, try an alternative server.
When the connection is established, you should see lots of text scroll past very quickly as the client catches up with the conversation. When this stops you will see a welcome message followed by something like:
/end of names list... or
You are now talking on #xwz_abc
You are now officially part of the channel and will see lines of text appear as the other channel members type their messages.
In one window will appear the nicknames of everyone on the channel, yours among them. Anyone with an @ symbol next to their nickname is the operator in charge of that channel. Operators or ops have the last say in all things to do with that channel. They have the ability to exclude you from the channel. Anyone who creates a channel is automatically given op status. The only other way to become an operator is to have op status assigned to you by the incumbent operator.
A main window shows all messages on the channel. Each begins with the sender's nickname enclosed in angle brackets. This is where automatic notifications of people joining or leaving the channel appear, as well as your own messages as you type them.
When you press Enter the message is sent to your IRC server and almost instantly appears on that channel throughout the world. Remember that the only thing people have to judge you by is your words, so choose them carefully. Netiquette dictates that you send a informal message whenever you join or leave a channel... a simple "hi all" or "bye all" will do.