How to use SFTP

I am using WinSCP tool and I am trying to log on to a remote server using SFTP.

I have a private ssh key.

1) How do I assign my private key to log into the SFTP server?
2) I didnt think I needed a username or password if I had a private ssh key..
3) Is there any documentation on how to do this on the winscp.net site?


Thanks for any help

Specify your private key here:
https://winscp.net/eng/docs/ui_login_authentication

You still have to specify an username (not a password though).