You might have been given server host key fingerprint. That's not for authentication.
See https://winscp.net/eng/docs/faq_hostkey

You typically need a password or a private key, unless your server uses some less used authentication method (like Kerberos).

I have a vendor I am working with. I am setting up a new connection to their test server. I have the host name, port number, and user name I need. They did not give me a password. They sent me a SSH Key Fingerprint in an email. I have looked through the site settings but do not know how I can authenticate using this plain text fingerprint. Is there a way? Thank you.