This is one of the most common questions asked by would-be writers.
Some years ago I was instrumental in the launch of a Creative Writing Course - back in the days when correspondence (distance learning) courses preceded online methods we see today. There was no internet. It involved a series of assignments which students completed and submitted for assessment at the end of each section of tuition.
Start with your life story
The first assignment was always 'Write you own life story'. Submissions varied and, for some, that was all they ended up writing. They had fulfilled their ambition.
But for all who completed the assignment it proved one thing: that they could write.
Of course, the quality of writing varied, which is where the tuition helped - from improving grammar and punctuation, through to developing the actual art of 'storytelling'.
Writing to publish costs nothing
Thanks to Amazon and Kindle Direct Publishing you can get an e-book out there at no cost, as well as a paperback, without going through the ritual of being 'accepted' by a publishing house.
Furthermore, you don't have to go through the kind of 'print on demand' (we called it 'vanity publishing') where you have to pay up front to be published. I have heard where some fellow authors, disappointed that mainstream publishers have rejected their book, have 'employed' a company to print and publish their book, on a limited initial print run basis, and have parted with several hundred pounds. (Aaaaaagggghhhhh!)
You don't need to do this. With Amazon KDP (and there are others), you can publish in eBook at no cost, and then to printed copies where you can order as few as ONE COPY (yes, you heard me) for (say) less than a fiver. Much less.
Sell yourself - or pay someone to do it for you?
If there is a downside it is that you have to market the book yourself. Even if you keep away from paid advertising (where I would recommend you do resist spending money) you may feel it worth publishing your own website - which is easy enough and cheap enough if you use online services like Wix. And you may have to learn how to get yourself out there on social media platforms.
How to become a novelist? - Set your sights high and your expectations low
The one constant throughout all this is that it is hard work but (as they say) 'if you enjoy what you do you never have to work in your life'.
Make that your main aim, by discovering how to become a novelist.
John Morey
Author of Finding Rose and Rose: The Missing Years - plus The Sign of the Rose (but only after I had written my life story to age 16!)