Age 65 is when you normally enroll in Medicare. Original Medicare consists of two parts:
There are certain health related conditions which allow Medicare enrollment before Age 65.
And you may defer Part B enrollment (without penalty) if you are still working and covered by a creditable employer group health plan. Different rules may apply if your employer has 19 or fewer employees.
You can make changes to your Medicare Advantage and Medicare prescription drug coverage when certain events happen in your life, like if you move or you lose other insurance coverage. These chances to make changes are called Special Enrollment Periods (SEPs). Rules about when you can make changes and the type of changes you can make are different for each SEP. Here's a list ... https://www.medicare.gov/sign-up-change-plans/when-can-i-join-a-health-or-drug-plan/special-circumstances-special-enrollment-periods
You can try to figure this out by yourself as to what plan or plans best fit your circumstances. If you are married, your spouse may not need the same coverage you need. You can Google the bejeezus out of this until you drive yourself crazy. You can go to a local senior center and get information there. Or, if you wish to speed this up, give us a shout and we'll be happy to help you.