Your user name is the email address you used when you signed up for your Coalition account. If you're not sure of the correct address to use to log in, try one you think is likely, and request your password if you have lost it.
If the system can't locate an account with that email address, try another possible one until you figure out which address you used when signing up.
Once you log in, you can add additional addresses associated with your account. See this article for more information.