To access a database QueryTree needs a database user with SELECT privileges to one or more tables/views. Running the following MySQL commands will create such a user:

CREATE USER 'QueryTreeUser'@'localhost' IDENTIFIED BY 'LoginPasswordGoesHere';
GRANT SELECT ON DatabaseName.* TO 'QueryTreeUser'@'localhost';

Remember to change 'LoginPasswordGoesHere' to a secure password and 'DatabaseName' to the name of the database you want access.

Don't forget that you do not need to grant QueryTree access to all the tables/views in your database. If you like you could create a set of QueryTree specific views and only grant the QueryTree user access to those.