The worlds folder on the server is located at ./universe/worlds/
You will want to use an FTP client to upload your world to the 'worlds' folder on the server.
Once you have uploaded your world to the server, You would edit the 'World Name' setting in the config.json using the config editor in the configuration files option.
It should use the name of the folder you uploaded to the world's folder.
The default world is named 'default'
