What nickname should I use?

Anything you want - at the present time the chat room is not linked to a database of nicknames, although this may come later.

How do I broadcast my A/V?

In order to start broadcasting your Audio and/or Video you will need to first turn it on. To do this click on the 'A' or 'V' buttons in the 'Me' pane below the text entry area,

The first time you do this you will be asked to grant permission to use your Mic and Webcam. The dialog box will look like this,

After you grant permission the AV will start. You will be able to see your own feed in the 'Me' area.