As an M1, the best advice I can give you is to just relax and enjoy what is left of normal life. Everything you need to know for the boards will be taught in med. school. If you have never had an anatomy course before then take an intro level one, but don't overwhelm yourself. IMHO you'd be better served learning clinically based things like taking H&P, BP, and reading X-Rays.
Just my 2 cents.