Just start writing. Write as much as you can as often as you can, and carry a notebook around with you so you can jot down ideas as they come to you. When you've written a first draft, read over what you've written and try to improve on it in your second draft. Also, read books and analyse how the book is written, what makes the story and the characters believable, etc. You don't need a degree in English or Literature to write, you just need a good idea and the talent and motivation to turn that idea into a book. Good luck
