Learn, Learn, Learn, Learn, Learn, and then Learn.
Then Learn some more.
Then practice what you have learned by writing the first draft of your story.
Why do I say this?
I say this because writing has a very large body of professional techniques which has been honed and improved over hundreds of years. If you start writing without learning about these techniques, it will be a much more frustrating, time-consuming, effort-intensive journey that it would have been had you learned how to write first.
Would you get on the football field without learning the rules of the game? Of course not!
These techniques aren't hard, you just have to know about them so you can practice them, the same way you have to know grammar and syntax so you can practice them.
The good news is that you can get a fairly solid introduction to these techniques by reading a few books about how to write a novel.
I recommend these books for your consideration:
Techniques of the Selling Writer, by Dwight V. Swain
"Techniques of the Selling Writer provides solid instruction for
people who want to write and sell fiction, not just to talk and study
about it. It gives the background, insights, and specific procedures
needed by all beginning writers."
The Creative Writer's Style Guide, by Christopher T. Leland
"Textbook rules about punctuation and grammar can be difficult to apply to your novel, short story, personal essay or memoir. There are special considerations that normal style manuals just don't address."
Outlining Your Novel, by K.M. Weiland
“Ms. Weiland presents a wonderful roadmap for writing while still encouraging you to take those sidetrips that will make your story better. I feel like I can walk the ‘high wire’ of my imagination because I have the safety net of my outline below it all.”—D. Hargan"
This next recommendation covers some very advanced techniques, but they are very powerful.
Anatomy of a Story, by John Truby
“Truby attempts to inform the entire story, addressing plot, character, tone, symbolism, and dialog. The key here is to grow a script organically rather than force the story into preexisting mechanics . . . Highly recommended.” ―Library Journal
Here's a video of John Truby:
Here's a video by freelance editor Ellen Brock. She has many good videos about writing on Youtube.