I got made fun of as a child by a parent for doing art and just... never did any ever afterwards. I primarily hang around artists tho and would like to relate to them more, but none of them do creative writing. I've read numerous grammar books, so that won't be a problem, but none really go in to how to construct a sentence, paragraph, page, chapter, plot, etc. I'll happily take any advice on the subject, really anything you can think for someone with actually zero experience.
Good advice I've gotten so far is to just write basically whatever. Also, people who are visual artists and creative writers, which was "easier" for you to become fluent?
I'm not an artist, I'm a programmer but I write a lot of docs.
Each writer has their own approach. Some like structure, then filling. Some like to explore individual stories with no specific end in sight, writing as everything happens in their minds.
You have to just start writing to find out what you like best, what's your favourite topics, what do you like about your own stories.
On technical writing, I start by studying the topic while making short notes of things I'd like to remember, or that need to be structured. Then I braindump it to find a structure that allows me to cover what I want for a given audience, then I add in the appropriate details for the use case.
If I were to approach fiction, I'd start with broad strokes, notes for the setup, main events, length, and where do I want to get with the story. Write some headings and start adding the filling with details. But that's me.
I'd suggest you exercise with simple non artistic short stories, random chapters, different scopes and sizes, to learn how to imagine and write naturally. Then maybe you start noticing some patterns on what you like to write. Then just go for it! It's the stuff we like that make each artistic work unique.
Good luck!