I'm sure Anthony (Candy Corn Apocalypse) can help with this one.
As for myself, I've only ever had work published once... in the pages of the MV Creations Masters of the Universe comic series.
But, having researched this a ton lately to prepare for launching the novel, I can say that I think you actually have a handful of options depending on your goals.
There are the two most common routes... self-publishing or traditional publishing, but there is a third: hybrid publishing. I had actually considered using a hybrid publisher to get the novel on the market quicker, while still retaining the rights so that if an agent/traditional publisher is interested, it can easily be moved to them.
If you're goal is a film or TV series, you might consider having the story adapted into a screenplay. I think it is much more difficult to get a screenplay seen by the right people, but if your short story garnered interest, at least you would have something to show a producer or studio.
I'm no expert, so please don't take this advice as gospel. I'm merely going on what I have read in researching these things.