With Medicare, timing is key. If you already get a Social Security or Railroad check for retirement, you'll automatically be enrolled you in Original Medicare. You don’t need to apply. If you're automatically enrolled, you'll get your Medicare card in the mail 3 months before your 65th birthday.
Do I need to sign up for Medicare Part A and Part B?
How can I sign up for Part A and Part B?
Otherwise, there are certain periods when you can sign up for Medicare, Medicare Advantage, and Medicare Supplement plans.
Medicare Advantage Enrollment Period