You will need to log into cPanel with your supplied username and password.
Normally this URL like: http://www.joomquery.com/cpanel. Select the Username field and enter your username. Select the Password field and enter your password. Next click the Log in button. Select the phpMyAdmin icon from the Databases section.
Select the database you wish to restore. Scroll down and select the Check All link. Now click the With selected dropdown list and choose Empty.
Scroll down and click the Yes button. This empties all our tables. Now click on the Import tab. Click the browse button.
Select our backup file previously created using phpMyAdmin. Click the Open button.
You now know how to restore a Joomla backup using phpMyAdmin