If you are already collecting Social Security, you will automatically be sent your Medicare card with Part A (hospital benefit) and Part B (outpatient benefit) in the 4th month before your birthday. If you are not collecting Social Security, you will need to go onto www.ssa.gov to request enrollment onto Part A and Part B. Your Medicare coverage will be effective the 1st of your birthday month.
Since Medicare was never meant to cover you entirely, you have two options to select from. Your choices for coverage to fill in the gaps not fully covered by Medicare Part A and B in place (1) Add a Medicare supplement/medigap policy to cover the medical copays not fully covered by Medicare that also provides you with freedom of choice regarding your medical providers, along with adding a stand-alone drug plan (the later is known as Part D) to cover your prescription drug needs; or (2) Select a Medicare Advantage/HMO plan (also known as Part C) that will cover both your medical and prescription drug needs. Whichever coverage you select will then be effective the 1st of your birthday month.