You can redirect your complete site (when someone type your domain) to another URL, placing the following lines in your .htaccess file in your public_html directory:
RewriteEngine on
RewriteCond %{HTTP_HOST} ^yourdomain.com$ [OR]
RewriteCond %{HTTP_HOST} ^www.yourdomain.com$
rewriterule ^(.*)$ http://www.newurl.com [R=301,L]
This will not follow the path, which means anything you type after the domain will always redirect to the new url. For example, someone typing http://yourdomain.com/myforum will redirect to http://www.newurl.com
If you wish it follow the path, for example if someone type http://yourdomain.com/myblog redirect to http://www.newurl.com/myblog, please check the Domain Redirection section in you cPanel, you can easily set it up that way from there.