Some hosting companies setup your domain name (www.yoursite.com) for you, but if you want to save money I suggest doing it yourself. Its not hard at all and only takes a minute of your time. First thing you need to do is ask your hosting company what their name servers are for your hosting account. Once you have this information you need to find a registrar and register your domain name with them. I recommend godaddy.com as a great registrar. After you register you will need to login to your account and click on the link that says change name servers. Fill in the form and your done. It will take 24-48 hours to propagate through the system. After 24-48 hours your website should be accessible through the Web.