clan chat is utilized in two ways. To maintain a conversation in clan chat you can start by typing
/c
followed by a space, which is will switch your chat box specifically to clan chat. Everything you type will be entered into the clan chat.
To switch back to public chat you can type
/p
followed by a space, and you will be switched back to public chat.
Alternatively if you do not wish to leave public chat, or find that switching between the two is tedious you can put a double forward slash in front of the message you wish to send to the clan. Example:
//Sup guys!
This will send the message into clan chat, but any message you type without // will still be in public chat.
25-Mar-2016 15:16:16