Published author here. Think of it as running a marathon. It takes a lot of time and effort to get good at it, and some people are naturally better at it than others. But there's no magic trick. You need something to write on, something to write with, something to say, and the persistence to say it. That's it.
My best advice is to set yourself a daily word count. 500 a day, 1000 a day, 2000 a day, whatever you feel is achievable. Show up even when you don't feel like it. Write even when every word is crap. Depending on your target, you'll have a workable first draft within four months to a year.
Then you need to edit it, which will take at least as long and be at least as difficult and will about kill you, but if you do it right, you'll have a piece of work you can be pleased with.
If your goal is publication, the odds are your first novel won't find a publisher (although it might). But you will have learned so, so much from writing your first one. Writing is like any other skill - the more you do it, the better you get at it.
Good luck and get writing!