How to login to server with SFTP

When I run winscp from command line with a script, how do I specify that I want secure ftp?

Evidently, I can connect to the server with "open sftp://servername". I assume this establishes a secure ftp sesstion. But then how do I pass the login/password? Using "open user:password@sftp://servername" does not work.

OPEN sftp://username:password@servername seems to work.