Your email address is NOT your username for the Media Control Panel! Stream101 has provided a username and password to access your account, which was emailed to you upon signup, and also is available in your Client Area control panel under My Services. If you have multiple streaming accounts, you will need to be sure to choose the appropriate one from the My Services page to ensure you are using the correct username.
You are also able to change the password from this same screen, by following the instructions from this knowledegebase article: I’ve lost my cPanel/Media Control Panel password – Help!
To access your account, simply navigate to the Media Control Panel (MCP) and enter your username and password to login.