How to emulate an IM

I’m trying to emulate an IM box so if you type something, that something would appear as if you actually sent an IM.
This is for a demo so it’s all just smoke and mirrors.
Like if I made an input box to type text in, then hit the send button and that would trigger a dynamic text box to display what was typed in the input text field. Think that’s how. Anybody have a chance for an example or possibly just give me some hints?

Thanks