In the name field place a name you wish to use. Then on the bottom right of the chat box under the "Go" button should be a link that reads "profile." It might be slightly cut off. Click it, and a new window will open. The window will note the name you selected, and then have the standard enter password and repeat it fields. "Save" it and you should be logged into the chat with that name.
When you come back and need to log in again put your name into the name field, then click "profile," then log in with the new window.
If you're having issues seeing the "profile" link, remember you can access the chat box by going to cbox.ws/?n=2-1944057-7525 at any time.