TL;DR Read some stories. Try your hand at writing some yourself. It's not that hard.
Flash Fiction is a short story that is typically 1000 words or fewer, and written quickly, over a few days. It's often done as a challenge to a prompt, such as a photo, a song, a mash-up of genres, or a random selection of keywords.
I used to be part of a site by the same name, here, and did 100 or so Flash Fiction back then. Some were good, some were meh, and I occasionally found a recurring character or theme in several that suggested a novel. I needed a push to get writing again, so I started my own site. I'll post a new prompt here each Friday, with the FF due by the next Friday, noonish.
The point of these prompts is to push you a bit, to get you out of a rut, or if you're new to writing, to give you a starting point. Don't worry about revising it over and over, just consider this a quick way to try out a new character or situation or genre. You may end up with just a part of a story, a scene, a fragment—that's fine. I know that there are many sources online detailing how to perfect your craft, but I'd suggest you initially keep it simple and just write. Pick a prompt and go. Outline, structure, character arcs, plot points, clever twists--all can come later. For now, you can just stuff your story in a drawer, or show it to a friend. Maybe to your mother. Praise is a good thing. Then talk it over with other writers, tweak, and the next one will be a little better, a little easier.
For this site, post your story on your blog, with a link in the comments of the prompt post. Critiques are encouraged, just be respectful. Say what you liked, then suggest what could be improved. The point is to practice writing on a regular basis, try some new things, get feedback, and improve one's work.
Note - stories are copyright by the author, and they retain all rights to their work.