*Disclaimer …
This how-to is going to walk you through setting up an FTP server. And then it’s going to suggest you don’t use it, because it’s not secure.
It may be a good idea to read (without doing) pages 1 through 4, then go back and do it. Then you can decide if you want to skip the FTP section.
This how-to walks you through using an https file manager instead of FTP, and the “Do more” section shows you SFTP, which is secure file transfers over ssh. It’s my opinion you should still learn FTP, but I did want to provide a disclaimer that after its setup, we continue on to not use it.