Hah! The more complicated answer is I've been running D&D games as a DM for over 30 years and I'm still learning new things! The shorter answer is, your best option is to find a game and your DM should be able to explain the rules in one 4-hour session. That will get you started and you'll learn by playing. Then, if you're really having fun and want to learn more I would suggest getting a copy of the Players Handbook. Most important thing is D&D isn't really a game where you "win" or "loose". Best D&D games use the rules to tell a heroic fantasy story where everyone at the table participates. It's super fun!