The education required to become a state trooper varies by state, but in general at least a year of post-high school education is required. In some states, if you have served in the military the post-high school educational requirement is waived because of your experience.
You can enroll in Medicare Part D coverage once you meet both of the above requirements. Your Initial Enrollment Period for Part D is when you're first eligible to sign up for prescription drug benefits, and this period usually coincides with when you're first eligible for Medicare coverage.
If you do not enroll during your Initial Enrollment Period for Part D, you can enroll into prescription drug coverage during the Annual Election Period (AEP), which occurs from October 15 to December 7 of every year.