Open the IRC client from the world open menu. You will see a window like this.

Before we can begin you need to configure your client. Click the "setup" button in the top row. A setup dialog window will be presented.

There are three tabs along the bottom edge of this dialog window. They are "Current Configuration", "Current Options" and "Profiles". The "Current Configuration" tab shows the current operating setup for your irc client. The IRC client uses profiles to manage your IRC connections. Let's create a new one. Click on the "Profiles" tab. Your profiles window pane should look something like this (although you will undoubtedly find other entries in it). The one shown here is empty.

There is a row of buttons you use to manage your profiles. The "add" button will create a new one for you. "delete" will remove the currently selected profile from the list. "edit" will edit the profile you have selected from the list. "select" will use the profile you have selected from the list as your current configuration. "Save current..." will store the current existing configuration (as seen in the "Current Configuration" tabbed pane) as a new profile in the list. Click the "add" button.
The first step you will need to do is select an IRC server. The following window appears.

The IRC client has a large database of servers you can choose from. They are divided into "groups". For this example select the group "<undefined>". Undefined is the group default if the existing server definition does not have a group name defined in the database. Then select the server "Open Projects Net". There's only one port available (6667) so choose that. Press the Okay button on the dialog window.

Now that we have an IRC server selected we see the "add a profile" dialog.

By default the "Profile Name" field has already been filled in with the name of the server we selected.
Replace the "Nick" entry with your own personal nickname for IRC. Note that this name needs to be unique. Don't forget to press the Command-S (Save) command after you typed in your nick.
For the "Full Name" field there are 2 parts. You enter in your full name and your email address
There's also a "Username" field.
The last entry field is also filled in by default with the actual device name for the IRC server you selected.
Here's an example filled in.

Press Okay and you will see your new profile added to the profiles list.

Select the profile and press the "select" button. Now when you choose the "Current Configuration" tab you will see your new selected profile is active.

Close the "setup for IRC client" window by pressing the "X" close button.
Press the "Connect" button on the IRC console window and the client will attempt to connect to the currently configured IRC server using your current profile.

Note that you cannot change the on-line configuration while connected. You can manage your profiles but will have to disconnect before changing the current configuration. The client indicates this in the setup dialog when you open it.

After connecting you should begin by clicking on the "channels" button. That will open up a new tabbed pane named "channels list".

It can take a while for this list to download from the IRC server. Scroll down to the channel named "#squeak" and select it. Press the "join selected" button just above the list and you will enter that channel.
The channel chat window pane looks like this.

It shows all public channel communications for the channel you selected. The main channel pane will accept direct typing as well as the narrow input pane along the bottom. Just be sure your mouse pointer is in one of them.
There's a lot to get to know when using this client on IRC. Some basic common commands are supported from the channel input pane. These include:
/ACTION text
/WHOIS nick
/CLEAR
/INSPECT
As you use the client there are many possible activities you can be involved in. The tabbed panes can be managed to help you organize your chatting.

There are several default tabbed panes and others added as you use the client. The current pane showing is highlighted with a yellow tab.
The "console" pane shows all IRC console messages. If something didn't work as you expected have a look at the console to see what was logged.
The "private messages" pane is a catch-all for any private messages that are not sent to a specific private message window. By default all private messages are sent to a tabbed pane having the name of the person sending you the private message. You can disable/enable this behavior in the options section of the setup dialog.
You can re-order the tabbed panes in this window. On the right hand side where the tabs are drawn are three buttons. The "<" button will move the currently selected tab one slot over to the left. The ">" button will move it one to the right. The "x" button will close the current pane. You activate a pane by clicking on it's tab. If there is activity in a pane while it is not active, the tab adds a light red highlight around it's edge. In the example shown private message pane from "sbw_" is highlighted to let us know that some text has been added to that pane while we were looking at the #irc-test channel pane. All channel related panes begin with the # character. Private message panes do not.