The official website for Medicare is: www.medicare.gov.
There is plenty to read at this site to get some information, but the devil is in the details so be careful and inquisitive. You can also call 1-800-633-4227 and say “agent.”
The on-line Medicare sign-up website is actually through Social Security at: www.ssa.gov/medicare/. You will need to read the rules to see if you are eligible to sign up online, and then scroll to the bottom and click on the blue button that says “Apply for Medicare only.” To call them directly phone: 1-800-772-1213
Once you are on board with Original Medicare, your services are provided by CMS. Their website is www.cms.gov and the phone number is 877-267-2323.
Another place to find information is the National Institutes for Health at www.nih.gov.