Hi mxomaskandi,
the plugin can work with a cloud player, getting the url in the JW Player Dashboard, or with a self hosted player, that means placed on you site.
If you decide to use this second method and only in this case, you have to say where the player is, jwplayer.js is the player.
Every method is fine for uploading files to the server, FileZilla (Ftp) for example.
