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One doesn't just choose to get into something, it chooses you. It sounds like you're wanting to pick up an interest that you're not really interested in, otherwise you wouldn't have to ask this question. Examine your reasons before proceeding and maybe find something that -truly- interests you before spending that time and energy you can never have back.
That said, ignore that your sources are for people who are already "into" something. Dive into the resource of your choice, read, and when you don't understand something, hop to Google or Wikipedia and read some more. If you want to learn makes and models and generations, Wiki is actually pretty damn good at cars, less so but still adequate with motorcycles. Go there, type in a make and model that you like, and absorb its condensed history. If it is something that you're truly becoming interested in, you can spend -days- doing this. Good place to start.