When I was new to Advanced Hosting, I got this exact same error, so I understand your problem. You have to create a MySQL database and user, then add the MySQL user to the database. This can be done using your cPanel account. After doing that, use this information, and you should be able to proceed further into the installation.
If you have any other questions, problems or concerns, please feel free to ask them, and I would be more than happy to answer them.
Thanks for listening.