Minecraft: How to make a multiplayer server based off a singleplayer world?

Basically, I want to know how to make a multiplayer server made off my singleplayer world. Is there any way to do this? And if I need to edit server properties, what program do I open it with?Minecraft: How to make a multiplayer server based off a singleplayer world?
First off, I am assuming you already know how to make a server that WORKS. That is very important. If you don't know, search for a tutorial on youtube. Ok, so click start, go run (search run, click it), type in either %appdata% or just appdata depending on what operating system you have (windows 7, xp, vista). Open the .minecraft folder. Then open the saves folder and all of your single player saves are there. Copy and paste the one you want to the folder where you keep everything for your server. Then, open the properties file for the server and change the world name to whatever your singleplayer world is called. Hope I helped.