1. Well, the IP address/hostname of your server. If you are testing the connection from the same machine, then "localhost" would do. But in real life, that is useless.
   
2. If you want to use key authentication, there's a section above that details it: https://winscp.net/eng/docs/guide_windows_openssh_server#key_authentication

I’m following the procedure at https://winscp.net/eng/docs/guide_windows_openssh_server#connecting2, and am doing to the “Connecting” steps.

In the new New Site dialog, I don’t know what to enter in two of the fields:

1. Host Name: Should I enter localhost, or something else?
   
2. Advanced Site Settings/SSH Authentication, Private Key File: What goes here? Am I supposed to create a key file (if so, how?). Or is the file somewhere on my machine already?