To enter the chat, enter your user name and then click 'Connect'. Once in the chatroom, type your message in the long white box at the bottom of the screen and press Enter.
You can choose any user name you wish. Some good choices are:
When you enter the chat, you'll see messages from people already in the room. If you're new to online chatting, take a moment to 'listen' to the room and get a feel for who's talking to whom. If you'd like to say something to the group, type your message in the long white box at the bottom of the screen and press Enter.