I don't think you should worry about your idea being copied. First, there may be other people who have had the same idea independently.
Second, the reason people say things like "ideas don't matter, execution is everything" is because any idea you think you have will have myriad assumptions baked in that will be unique to how your mind works. Other people who nominally have "the same idea" won't really have the exact same idea. (This is why there are, for example, so many Christian sects: because millions of people who call themselves Christian have different ideas about what it means to be Christian, as hopefully a relatable example.)
Just start by putting up a web page or creating a github repo or similar and maybe tweet it or post it to HN or otherwise share it through whatever channels are comfortable and familiar for you. Unless you already have well developed channels where lots of people are very interested in everything you say, it can be surprisingly hard to get any traction. You are probably overestimating the attention your idea will receive.