The easiest procedure to import your old world files is as follows:
- Compress/archive your "world" folder to a zip-file. If you are importing a singleplayer world, see below where your world files are located.
- Go to your server at our server panel, then to the "File Manager" tab.
- Upload the zip-file you just made by simply dragging it in to the browser window in the File Managers root folder (the folder where the server.jar, server.properties and whitelist is).
- Mark the zip file, then click on "Unarchive".
Now, your world is uploaded and you can start your server!
Minecraft singleplayer game worlds are stored in:
Windows: %appdata%. minecraft\saves\
GNU/Linux: ~/. minecraft/saves/
Mac: ~/Library/Application Support/minecraft/saves/