Take the MSF Safety course and also the road course if they have one (where you go on street with instructor ).
Ignore all advice from idiots saying your too big for that bike or things of that nature, not true. 300+ men ride fine on a 250cc. Start out with a small comfortable bike like 250 - 500cc bike used with miles on it. My first bike had over 60K miles on it and ran like a champ until it was totaled. After that experience if a bike is well taken care of I have no problem buying one with high miles.
Life is about risk, I messed myself pretty bad, going at low speeds, new rider mistake also I cut cut off in another incident which totaled. I will ride again just now now, but the risk is there and serious you have to be safe smart, and assume people don't see you and if possible ride in groups / group rides, and if your going / insistent on a "crotch rocket" of any kind. I highly recomend you take corner speed course or a a track day at your local track to teach you how to ride it and well. All the best and good luck. cheers.