First set the source and destination file path and name (you can use a variable) and select whether the source file is on a remote server or the local server. If it is on a remote server, click the Is source remote? checkbox.
For remote servers you will also have to select the Configuration which contains the connection information (IP address, User, Password & Protocol).
The non-remote server side of the transfer only needs the file path and name. You can actually initiate a file transfer between two remote servers, one to the other. In that case, both sides of the transfer would be flagged as remote and both would require the Configuration to be selected.
Like with other configurations, you can only set one FTP connection so if you have more than one FTP site you need to connect to, you will need to create multiple configurations.