Go to your cPanel and click on phpMyAdmin in the Databases box.Once in the phpMyAdmin select the Joomla database from the drop-down menu at left. The page will refresh and the database’s tables will be displayed on it. Open the SQL tab.
In the text field write the following SQL query:
UPDATE `jos_users` SET `password` = MD5( “new_password” ) WHERE `jos_users`.`username` = “admin” ;
“new_password” – replace this with the new password you wish to use.
“admin” – replace this if your admin username is different.