Start NOW. Plan on applying 2-3 months before turning 65. To begin getting a basic understanding of Medicare, and the choices you need to make, download the Medicare annual handbook called "Medicare and You" at
https://www.medicare.gov/forms-help-...ferent-formats
You can also order a hardcopy.
It will acquaint you with all the terminology, and the major choices of plans and coverage.
Then come back here and ask about specific issues you don't understand.
Be aware also there are local resources available to you for help also. They are called "SHIPS, and are explained in the Handbook.
Take it slow. There is a lot to understand in order to make the best choices that work for you. It is not "one size fits all".