You need to edit wp-config file
WP-Config.php is probably the single most important file in your entire WordPress installation. This is where you specify the details for WordPress to connect your database. If you changed your root password, or the database user password, then you will need to change this file as well. First thing you should always check is if everything in your wp-config.php file is the same.
define(‘DB_NAME’, ‘database-name’);
define(‘DB_USER’, ‘database-username’);
define(‘DB_PASSWORD’, ‘database-password’);
define(‘DB_HOST’, ‘localhost’);