Accept the download for the Javascript client thingy if it shows up.
Wait for the grey box to turn white and ask for a nickname and channel. Refresh the screen if it takes way too long.
Type your screen name in the appropriate box and leave the channel at #rebels.
Click the Join button and wait.
If it warns you that another person registered your screen name, change it by typing in a new name before 60 seconds are up, or it will kick you off.
You will be able to see a list of all the people in the chat room on the right hand side.