Log in to cPanel using your username and your cPanel password at http://yourdomain.com/cpanel,
where yourdomain.com is your domain name.
Click on Backup Showing in Files Menu
As currently there is no any generated Backup at this time. To take backup click on Download a Full Account Backup.
After click you will see Progress Bar which shows backup is started succesfully.
Once backup file is complete it will show you in backup menu as now this file can be downlaodable by just click on the file name.