This question is a very open one and i'm not sure what exactly you need to know but you'll need to do a lot of planning. Generally you need to develop an idea of the setting, plot line, characters and the overall meaning or topic of the story. It really helps if you know how you want the story to end so you can create plot twists and use foreshadowing to hint at future events. Most importantly you need creativity and inspiration, write something you think you would read if you were looking for something to enjoy.
