First, go directly to the carrier site, and log in there. Be sure to enter the password, and not allow it to pre-fill for you. If the login does not work at the carrier site, it will not work in EZLynx. If the carrier site displays a message that your password is about to expire, you will need to go ahead and update the password, then set the new information in EZLynx.
Once you are able to log directly into the carrier site, go to the Settings tab in EZLynx, then Carrier Logins. Simply click the Clear button, then Add/Set and enter your carrier username and password. Once you have a successful login set, which is indicated by a green checkmark, you can submit quotes to the carrier.