You'll need to do this through server manager. If you have IIS installed already, select that role in Server Manager and in the right hand pane, scroll down to "Role Services" and select Add Role Services. When the wizard comes up select the ftp server, ftp service, and ftp extensibility options. Once it's installed, you'll be able to manage the FTP site in IIS. Accessing it can be as easy as typing
ftp://servername in a web browser, but you may want to download an FTP client like Filezilla or CuteFTP.
