How to change name while chatting in chat rooms?

I hope someone can help. When chatting on like big brother and you go in with a chat name and you want to change it, I've seen people type in so and so is now known as so and so. (example) How do they do that???????????????????How to change name while chatting in chat rooms?
If you are using Yahoo Messenger 8.1.0.249 , Click on messenger/my contact details/fill in the information you want it to say/save and close, and/or add yourself to your contacts, and go to your name and change it to whatever you want. You can also click ';my profiles';, then click edit on the profile you want to change, then change your ID from your name to the ID you want to use. Messenger HELP link: = http://help.yahoo.com/l/us/yahoo/messeng = Messenger HELP link