Hello! If you are able to login to the account or access the previous user's email account, you may update the username and password in the "Settings and Billing" section. Some instructions cane be found here: Resetting your username, password and time zone
If you are unable to login, please contact our support team to verify the account details. We can then send a password reset message to an alternate address so that you can login and update the user information as indicated above! You can reach us at 800-595-4401 x1, or make this conversation private to provide your information securely!