Which FTP server software you choose is dependent on your system OS. IIS is not required even for Windows. There are many alternatives to IIS for FTP services such as Filezilla and others listed by Wikipedia. As previously mentioned you will need a public IP address. You should also make sure the server is as secure as possible and all patches applied regularly. I would also recommend shutting off "anonymous" ftp and ensure that only named users can login to access files.
if it is over internet, you will need an IP, then you will need to have iis installed and also configure the FTP site…that is about it….