Looks like your domain is not pointing to WordPress.com name servers yet. Please go to your domain registrar's site and log into the control panel. You will need to update the name servers as below:
NS1.WORDPRESS.COM
NS2.WORDPRESS.COM
NS3.WORDPRESS.COM
For more information, please visit the help documentation provided by the registrar and our support page:
http://en.support.wordpress.com/domain-mapping/map-existing-domain/