Fiction is made up. It may be based on real people, places, or events, but it is not true. It never happened.
I feel there are two ways to write fiction.
1. Plot out your story on paper in outline form, then write it using the outline as a guide.
2. Sit and write.
Many people think that one is better than the other, but that is not entirely true. Plotting needs to be done whether you do it up front or go back and fix the holes after having written the story. It all depends on what works best for you. Try it both ways to discover which you like best.
Good fiction needs at least four ingredients.
1. Backdrop: This is the setting of your story. Is it sunny Malibu? A space station on the moon? A fictional land like Narnia? England 1834? Spend some time thinking about where your story is going to take place. Do a little research if this is a real place to help with your description. If this is a fictional place, spend some time inventing details. Details, whether you use them all in the story or not, will help you as the writer tell the story better.
2. Characters: You need to invent interesting characters. They don’t have to be perfect, in fact a flaw or two makes them more realistic. A good place to start is with a character chart.
3. Plot: This is your story. Something had to happen to have a story. The best formula I can give you is to give your main character a problem that they need to solve. Without a problem, you don’t have a story.
4. Conflict: Your main character needs to struggle. That is what will keep people reading. Don’t let your main character solve the problem until the end of the story.