Your first step, if you didn't provide that information when you signed up (like if you had registered the domain after creating the site), then you'll have to contact us and tell us the new domain you wish to utilize.
Next, you'll need to update the "A Records" for your domain name and point them to 64.182.103.44. We currently do NOT provide DNS services, so if your domain registrar doesn't support DNS services, we recommend DNS Made Easy.
---- The day Microsoft makes a product that doesn't suck is the day they make a vacuum cleaner.