You must possess decent writing skills in order to write fiction. The best way to develop these is to read a lot of fiction and other materials to understand the structures in which writing can be composed. It will also help you in gaining knowledge about various fields of life which is never bad for a writer of any kind.
The world has been different during different eras. You must have knowledge of history and understanding of how the culture was back in the day and what were the norms of life.
Understand the thought process of the people so that when you write, you have a good idea about the whole affair and can mould your mind accordingly.
Select a topic with which you are at home, and have some good knowledge about as well.
Do keep in mind that selecting something which you have little information about can become a nightmare for you. Pick topics that can be thoroughly researched and have enough historical narratives.
Make a plot keeping in mind the details of the era which you are writing in. Make sure that the characters appear to fit in their roles and the setting is also correct. This will lend authenticity to your work.
Once everything is in place, you need to execute the whole thing. It will not be an easy task and you should be careful about it. Make sure that there are no loose ends and the characters and the story gel together well. Also try to keep it realistic to a large extent since too much fiction can sometimes bore the reader.
Check and Recheck
Many authors go over their work over and over again not only to remove mistakes and errors but also to improve upon the style and structuring. This can make the story all the better.