Lots of people start writing novels in their teens. Most of them are not very good at first. That is to be expected. A novel is one of the most complex forms of art that can be created by a single person. After all, a novel has to entertain a reader consistently for ten or twelve hours. What other work of art has to do that? For most people, it takes a long time to learn all the ins and outs and get good enough to produce publishable work.
Consider this: If you are serious about writing and publishing novels as a hobby or as a career, the novel you write at 21 is going to be a lot better than the novel that you write at 14. And the novel you write at 28 is going to be a lot better than the novel you write at 21. Rushing to publish at 14 could impact your reputation going forward. Chances are that if you do publish now, that book is going to be an embarrassment and a hindrance later in your career. Would 14 year old you want to live with the published work of 7 year old you? If not, give yourself some time to grow in your craft before you think about publishing.
But can you? Sure, there is nothing to prevent you from doing so. You can self publish, of course. There's a ton of information online about how to do that. You will almost certainly need your parents to sign any contracts involved on your behalf, but other than that, no one is going to stop you.
You can also submit to agents and publishers. They will judge you on the quality of your work and the professionalism with which you approach them. (Read up on the process before you begin. Again, there is a ton of stuff on line.) Frankly, publishers love any angle they can use to promote a book so if a 14 year old comes up with the next War and Peace, they will jump at the chance. But the odds of a 14 year old writing the next War and Peace are astronomically long. Once again, you would need your parents to sign any contracts.
But think twice about trying to publish the work you create at 14. You are learning, and that learning takes a long time. Focus on getting better at your craft -- and on accumulating a bit more life experience to put into you work. It will pay off for your career in the long run.