FTP over TLS
Open the admin interface, and go to settings. Choose SSL/TLS settings, and choose to generate a new certificate. The two digit country code can be found by googleing (United States is just US - it can be confusing that two digit can be two letters, and not necessarily two numbers only).
Once you have generated the certificate, and chosen where to save it, filezilla will auto fill in the private key file, and the certificate file fields to point to the generated certificate.
At this point, you can either choose to allow SSL/TLS if the user opts, or you can force them to always use SSL/TLS, and not allow them to connect if they do not use it.
I am not 100% on the force PROP P stuff, so I am going to leave this blank for someone more informed to discuss.
If you want to connect to a server using SSL, then your ServerType field for that connection needs to be set to FTPS.