There are a couple ways to start, but the surefire method would be to learn to program. It's (IMO) the easiest of the core skills to get decent at. (Or rather, it's the one where you can get the greatest payoff even if you're kinda crappy at it.
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But programmer or not, you need to consider what it is that you can make that will get people so excited they'll want to share in your vision (donating skills, donating money, or donating publicity so that others donate skills or money). You probably already know that an idea likely isn't enough; there's already a surplus of those floating around.
But there are a lot of things that are halfway in between a mere idea and the game you want to make. There are more tools than ever to allow non-programmers or semi-programmers to get their ideas out there (RPGMaker, Twine, PuzzleScript...), and lots of games begin as mods of other games. Can you make it out of cardboard? Can it be a module of a pen & paper game? Can you build it within a MUD? Whatever you can do, get it out there and let it succeed or fail. Then do it again and again.
(If none of those are good enough to capture your unique vision, then it's back to path #1: Learn to program and a lot of obstacles drop away.)