First of all the days of "sending it off" are pretty much dead. You can send it via e-mail nowadays and it works out peachy. Get yourself together a list of magazines you'd consider being published in. Google those magazines and you will probably be able to get the Editor's e-mail. After that just start sending your story to them. Take it one publication at a time and don't get discouraged if you get rejected. Trust me, it will happen. Just keep plugging away.
Be aware that different publications pay differently. Some will pay you cash. Some will pay you by giving you a free subscription to their magazine. Others will pay you in copies of the magazine itself.
You want to make yourself up a Bio Sheet and send it with every submission. On it have your name, pen name if you're using one, e-mail address, actual mailing address, and a short biography of yourself. The biography will give the readers an idea of who you are and how and what you know about the subject you're writing on so make sure you include some experiance on the subject.
Hope that helped a little and good luck.