This is something that I have also wanted to do for a long time, but have not. I’m sure that there are other published authors that can give better advice, but mine would be to just start writing and see where it takes you. Sure, it’s not gonna be a bestseller or even very good unless you are a prodigy, but it will give you a feel for how it is done. Getting your story in the hands of others and listening to feedback can also be invaluable. If you have written a short story that you like and got good feedback on you can also submit it to websites that publish short stories. Just Google “East of the Web” and look at the short stories written by other people for inspiration.