Change Default site on wordpress multisite

In order for sub-directory multi-site to work, it needs to modify the mod_rewrite rule (i.e. .htaccess file). Do you simply added the two lines in the wp_config.php or crated a WordPress network as described here?

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)