How To Connect Remotely To FTP Server

Ok I'm using my notebook along with smartftp to connect to the server running on my desktop. I can connect to the server from my notebook using the local IP of my desktop I presume. Can anyone explain to me what I need to in order to connect lets say from a remote computer in Chicago? What IP should I be using, etc? If there is anything else I need setup please let me know also.

Please advise and thanks in advance.