4. How do I enroll in Medicare Part A? Posted on September 11, 2017 at 11:57 am.Written by advantage_admin In Puerto Rico, you get automatically enrolled in Medicare Part A at no cost to you if you are a citizen and have worked for 40 quarters or more. If you have not worked for 40 quarters and you wish to enroll in Medicare Part A, you will have to pay a monthly premium of up to $413.00 for 2017. To learn who is eligible or to obtain more information, please contact the Social Security Office. Post navigation 3. What is not covered by Medicare Part A?1. What is Medicare Part B?