Weeeellll, find something that interests you, and then take a course on it at a community college or similar. Start small, work out from there. Longest journey, one step, and all that.
History? Drama? Music? Art? Writing? What are you
passionate about?
History is a good one. I love history, that's why I'm choosing it.
Another guy who is passionate about history is Dan Carlin, who has the Hardcore History podcast. These are fantastic programmes, discussing parts of history you may be unfamiliar with. I thought I knew a lot about Rome, but his five part talk about the fall of the Roman Republic (which included a marathon five hour final part) was just great, as was his take on the Mongols. And I'm about to start his take on WW1 (fact: did you know that in Sarajevo, the spot where Gavrilo Princip fired the shots that assassinated Franz Ferdinand has been immprtalised with metal footprints? This scandalises me, as those two shots meant most of the 20th Century was on fire, or close to it, even the hottest of fires, over Cuba. But I digress). If this is something that interests you, check his stuff put, and go from there. And there is a LOT of history to explore. And if you're into SF, as I assume you are, you can't help but think about alt.history, and knowing the real stuff will only reinforce that (see the Hardcore History podcast, 'The What Ifs of 1066').
Drama is also a good one. When a local theater group couldn't find someone to play the villain in a musical, my GF thought of me (yes, that kind of relationship), and not only did I learn some new skills, I had fun and met new people. What's not to like?
And important advice: get out of your comfort zone. It may sting sometimes, but at the end of the day, you won't regret it.