You can redirect all of the requests for yourdomain.com domain to http://www.yourdomain.com by modifying your website’s .htaccess file. You need to add the following lines at the beginning of the file in order to setup that redirection:
RewriteEngine On
RewriteCond %{HTTP_HOST} ^yourdomain.com [NC]
RewriteRule ^(.*)$ http://www.yourdomain.com/$1 [L,R=301]
Where yourdomain.com is your actual domain name.
You can edit the .htaccess file using the File Manager in cPanel or via FTP.
From now on, when someone access http://yourdomain.com the visitor will be redirected to http://www.yourdomain.com.
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