I'm using Vista TN3270 as my emulator. I'm trying to submit JCL jobs to it using FTP. I'm trying to follow https://www.ibm.com/docs/en/zos/2.1.0?topic=jes-steps-submitting-job-automatically-receiving-output but I don't know how I can setup connection between my FTP and 3270 emulator.
You can't! TN3270 is IBM's 3270 Display Data Stream SNA protocol over TCP/IP. The emulator supports an own protocol for file transfer which is based on TSO/E IND$FILE. This has nothing to do with the FTP(S) protocol.
You need to use the FTP client on your PC to connect to the FTP server on the mainframe.