In Google do a search for "Webmasters Tools" You will find Google Webmasters Tools and Yahoo Webmasters Tools, and Bing Webmasters Tools. You need to register
www.yourdomain.com and yourdomain.com in all 3 of these. You will need to create a e-mail account with each of them to get access to each one of their Webmasters Tools.
You will need to submit your www and non-www web address to all 3. But in Google you can also specify your geographical location. (recommended) You will be expected to put either a file or meta tag in the header of your domain, so that your website will be verified by Google, Yahoo and Bing. That is 3 different meta tags to install.
Also while we are on website optimization put this meta tag in your header as well.
<link rel="canonical" href="
http://www.yourdomain.com/"/> Just change your domain.co to what ever is appropriate.
Last but not least, Do a search for edit .htaccess so that only the www address or non-www address is the only accessible address.
Most www edit the .htaccess so that the non-www will not list but if you have a blog site you would go with the non-www. At least that is how I understand it all.
Hope this helps. Big topic for one forum posting.