itch.io

Maybe you could start with building a GDD (Game Design Document), that details all of your gameplay, mechanics, level design, characters, story, etc and can include technical details like the engine you want to use, the genre, estimated development time, the exact skills youll need (and how many individuals to fill those skills), how you plan to handle marketing/publishing and if you have any kind of compensation plan in place - even if your GDD is just a Google doc, Notion doc or even an update to your post here that just lays out the basic details can help a lot, it doesnt have to be hundreds of pages like standard GDDs tend to be

If you are interested in learning some coding skills as well, maybe you could start with an engine like Unity (imo its the most beginner friendly engine, others might find Godot or GameMaker also good beginner friendly engines) - once you know the engine you want to use, you could study the language that engine supports - for example, with Unity, it uses C#, if you wanted to use Godot, they have their own language called GDScript (some say its similar to Python), and GameMaker also has their own language called GameMakerLanguage (some say its similar to JavaScript) - theres a site called "w3schools" which have great and free courses for beginners on all those languages (C#, JavaScript, Python and more)

And small sidenote: I would maybe try to aim for a short prototype (which is often smaller than a demo), as often even the best ideas on paper play out differently once you get to actually play around with the idea in-engine, and having some kind of video you can record of the basic gameplay can also help for getting others interested in your idea, you can also add watermarks to any art you post online if you might be worried about theft - best of luck with the project!