As an independent, you should be able to find an
IMO that does some sort of Medicare training.
As captive, most carriers have classes they give their agents.
For self study:
Read the Medicare and you book. That overviews how Medicare works.
Read carrier materials. All
MA plans have to show how their plan works compared to Medicare in their summary of benefits.
Read this forum. Lots of info.
I also have a guide I wrote for agents getting into the market. I have not worked on it much since my purchase of my XBOX 360, but still has some good info. Shoot me a PM and I will email it to you.