When you say that you have “two different databases connected to the second one” What does that mean? I think I will help better if I understand what you did.
If I am correct, you will need a separate MySQL database for each blog you plan to install and a second WordPress install as well.
The wp-config.php file will vary for each installation. The lines to change are:
define(‘DB_NAME’, ‘wordpress’); // The name of the database
define(‘DB_USER’, ‘username’); // Your MySQL username
define(‘DB_PASSWORD’, ‘password’); // …and password