Having trouble using IRC

Ignoring what Warrfork said (since you already knew that information),

Etiquette for IRC: http://www.livinginternet.com/r/ru_chatq.htm (informal rules)

IRC commands: http://project89.com/quakenet-commands-cheat-sheet-8/#generalcommands

Now, since you were using webchat, certain commands are available by clicking on someone's name. These will appear before a person's name.

whois ~ gives you addtional information on the person
query ~ lets you "PM" a person. Basically creates a tiny private channel that only you and that person can use.
slap ~ gives the person a "slap". Basically it's used for grabbing the attention of someone you wish to talk to (don't spam it). (There is another way to get attention, see below)
kick ~ kicks a person from chat. Can't do it if you don't have OP status (the @ sign next to someone's name)
deop ~ takes OP away from someone. Same requirement as kick for use.
voice ~ gives Voice to someone. This lets them speak if the channel is moderated (+m is set). Same requirement as kick for use.

To type something, you can simply type in the chat box at the bottom and press enter. Your sentence can not start with a \ or / because that the sign for the start of a command.

If you wish to get a specific person's attention. You can include their whole name in the message you send. This will ping them. You'll see what that looks like if someone includes your full name in a message. You can have chat complete the name by pressing TAB after typing the first few characters (this only works if the characters you typed are unique to one person only. If there were two people in IRC, named Joesph and Johnny, typing Jo would not be enough. You'd need to type in one additional character for it to auto complete the name for you.)

 

Well, by default, when clicking the tab that says IRC on the ribbion at the top of the forums, you'll join #kag.

However, lets say you want to join quakenet (this is the server/chat service #kag is in. If you use a different server like FreeNode or Synirc or whatever, trying to join #kag will put you in a totally different room, not the one you are looking for) by using the default page for webchat. You'd go here then: http://webchat.quakenet.org/

There you'd be able to join by typing a nickname (if someone else on the quakenet server has the same name, you won't be able to use it, so you'll need something else) and typing the channel in the channel box using the format #channelname.

Now lets say you want to join another channel while using webchat. You will not need to open a new tab and do this again, instead all you need to do is type /join #channel2name. A new mini tab will appear at the top of the client and you can switch between the 2 by clicking on them.