Looking to do it as a career? If so then you should use Reedsy (free to use pay for services) or Scrivener (Lifetime license and it's widely used in the industry).
Looking to goof off? Wattpad or Deviant Art.
looking to improve or exercise your skill? r/writingprompts is a good place to flex your story muscles.
@Hitspark what if it is not to goof off but to write something that you think is interesting but not as a a career. Also wattpad and devian art seems like to have a bunch of smelly poo poos in there (my experience at least withy percy jackson fanfic)
@asianskill
Wattpad duhh... Try it, there are so many good amateur writers there. It's diverse when it comes to fantasy, romance, thriller, medieval ages, etc.
Plus If your writing really good you might have a chance Publisher will notice your work and invite you to become established writers. Seriously I see so many writers end up publishing their own novel from there