Peter, the usual advice is to research the market first and then write a short story to suit your target. But you can just as easily do the opposite.
It’s virtually impossible to find a mainstream agent or publisher who will handle short stories, no matter how many you have written.
I would suggest you start off by trying to place your finished one with a magazine. Is it one of the pieces you have uploaded here? perhaps we could have another look at it with a view to suggesting possible markets.
You’ll find oodles of short story competitions on the internet –
http://jbwb.co.uk lists dozens. Not all of them pay much and, obviously, the higher payers attract a higher standard to compete with.
http://www.cherrybite.co.uk run a quarterly comp where the editor selects the best (in her opinion) three entrants and publishes them anonymously in their quarterly magazine. The winner is then chosen by the readers. The comps seem to be her source of material for the magazine so, even if your story isn’t shortlisted, it still stands a chance of being published. She only pays a nominal fee but you get lots of valuable feedback from the regular subscribers.
Hope this helps.
Dee.
<Added>entrants? I think I mean entries...