To sign up for Medicare, you can visit the official website of the U.S. government's Medicare program. You can also enroll by phone or in person at a local Social Security office. The initial enrollment period for Medicare starts three months before your 65th birthday and ends three months after the month of your 65th birthday. If you miss this initial enrollment period, you can sign up during the general enrollment period, which runs from January 1 to March 31 each year. It's important to note that there may be penalties for late enrollment, so it's best to enroll during your initial enrollment period if you're eligible. For more detailed information and personalized guidance, you can contact the Medicare program directly or visit their official website for step-by-step instructions on how to enroll.