It is legal in the US state of Oregon, and I think maybe one or two others I can't recall. You start by finding a doctor who specializes in the therapeutic use of psychedelics, and giving them a call! Watch How to Change your Mind by Michael Pollan.

Be safe, be smart, and consult a professional. I don't recommend doing it "street-style" where you buy it off the black market and take it at a rave :)