By default a new world is generated the first time a MineCraft server is started.
If you wish to upload an existing world to your server, follow these steps:

1. Log in to our Game Panel (http://cp.roxservers.com) 
2. Click on Gaming Services > Your Minecraft server 
3. Stop your server (preferably using McMyAdmin, as it will grecefully shut down your server) 
4. Click on File Manager. (You can also do this via FTP if your world is large) 
5. Upload your world (preferably in a .zip format if using the file manager or "as it is" if using FTP) at the root of your game server files. The Single Player world should be located in: C:\documents and settings\USERNAME\application data\.Minecrate\saves or C:\Users\USERNAME\AppData\Roaming\.minecraft\saves 
6. If you already have a folder name matching your uploaded world, rename or delete it. Another option is to edit level-name in server.properties, which points out the world folder to load. You can edit server.properties in our Game Panel, by clicking Default Config Files > Config Editor for server.properties. 
7. If you uploaded a .zip version of your world unzip it using the drop-down-menu to the right of the file name) 
8. Once unzipped, start your server and you are done!