Help me start building rather than getting stuck at thinking.

It's been a quiet while that I have just been chasing the shiny object/idea. Doomscrolling through advice, tips, tricks, workflow, system, and whatnot. I want to know how to actually validate an idea, build, and improve.

Let's say I selected an idea; how should I approach it??

1. Starting making content on X or Instagram?

2. Posting on Reddit (I don't know how and don't want to spam)

3. Talk to people? (I am a kind of introvert, trying my best not to be.)

4. Or what????

Seriously guys, help me get out of this loop.

Also, whenever I have a good idea, I research; I find it's already there, and then my mind is like, "How would I compete with that?" and I am back to square one.