My Site Has Http://www.mydomain.com And Http://mydomain.com - How To Fix?

Doing SEO Scores etc, and several of them stated that I could be listed as duplicate content, because I have both http://www.mydomain.com and http://mydomain.com - How is something like this fixed? I want them to be www. Thanks!

If you have canonical url on the homepage which is always http://www.mydomain.com, this will not be a problem. Also if your http://mydomain.com site redirects to http://www.mydomain.com, this is also not a problem for you.

Okie thanks. Yeah if I don't put www in front, it automatically does it (on the homepage anyways). A couple of the SEO score checking sites said I had both