In your /include directory is an ost-config.php file.
This file contains the database connection information.
Scroll down to the section that looks like:
#Mysql Login info
define('DBTYPE','mysql');
define('DBHOST','localhost');
define('DBNAME','database-name');
define('DBUSER','username');
define('DBPASS','password');
Ensure that this sections matchs your MySQL server, database name, username, and password that you set up for OSTicket in your MySQL server. If they match then check the file permissions on the file. How to do this varies by OS. If they do not match then make them match and try again. If it still doesn't work then consult the MySQL logs and PHP logs to see whats happening.
