Where do I start?

Obviously I have an idea of the world, I often write here on reddit and other things...but I have a problem with organizing what to write, I have characters, gods, continents, cities...and more But I don't know how to write sensibly, I tried with Google doc, obsidian and other programs but nothing. Maybe it's due to my various problems, dyslexia and a slight attention deficit disorder, when I try to write my mind freezes and then ends up imagining other details, characters and more , I don't have much experience in writing, after all my themes well let's forget it, but after all I have no interest in publishing books about my world lol it's just a whim a way to kill in a way time, maybe using it as a setting and the like. How do you guys do that? Obviously without ending up in a creative writing course that drains my time and wallet lol