A Fog chat primer:

...If you see a blue figure to the right, you're equipped to enter the Fog. If not, first check that Java is enabled in the browser Options Menu. As a last resort, download a new Java-enabled browser.

...select a color by dragging the blue square

...enter your name and press the Return key

...click anywhere in the framed area on the right, type and hit the Return key to make your text visible to everyone.