It's easy to strike up a conversation with somebody at the gym. Look for a guy about your age who's not super-built, and just say: "Excuse me, can you show me how to use this machine?"
Most people enjoy sharing their knowledge with other people, so it shouldn't be hard to get somebody to help you. Just don't ask them to spend five hours showing you every machine in the place. Let them go after a couple of minutes, unless they offer to show you more.
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I'm not autistic, although I do not consider myself neurotypical. I've been diagnosed with major depression and socially avoidant personality. Bonus: bipolar disorder.
~My soul must be iron, because my fear is naked.~