Just write.
That might seem like half-assed advice, but really that's all you need to do. Find an idea or something you want to play around with and start writing. A lot of writers, especially new writers, get caught up in the planning stages and end up never writing.
I reccomend writing now and making stories later. Take up some fun short writing exercises (100+ words), such as describing the weather in interesting ways, etc. Short writing exercises are a great way to improve your writing and develop your style.
You shouldn't just write what you want published, or write your final project. You should write like an artist sketches.
As for actual story development, that mostly depends on the kind of story you want to write. I suggest looking at genres and themes to start with and use those to craft your setting and characters, and through them you can develop a plot.
But there really isn't a perfect formula for writing stories, it's an art so the journey each writier takes is different.
Over all, I recommend you focus on improving your writing skills through practice daily (or whenever you can) writing sketches. And find a story you want to write and develop characters, setting, and a basic plot for that story.
Don't get too hung up on details in early stages. Just have fun and write, and worry about editing and perfecting your writing after the first draft is finished.