chat

call me stupid ... but can someone please tell me how to chat to my opponent whilst playing???

Type what you want to say in the box and press enter. Some opponents don't want to talk and disable chat.

in Live Chess?

What happens if you click on the Main Hall tab? Do you see conversations and get a one-line box to type in?

Should be at the bottom of the game screen, however depending on your screen resolution it might sometimes get pushed off the bottom of the screen.  If you can't find it just below where the chat shows up, you might want to try resizing and/or moving the game window within the browser frame.

This box right here:

Inside that box:  A vial of poison and a hammer that's triggered by the detection of the decay of a single radioactive atom poised to break that vial.

Oh, and also: Schrödinger's chat.