Once an SSH connection has been established to ssh.afn.org, enter your AFN username at the "login as: " prompt.
The first time you log on, you'll get a warning message similar to:
The authenticity of host 'freenet1.afn.org (126.96.36.199)' can't be established.
RSA key fingerprint is 42:90:da:2b:8b:1b:21:43:d3:8b:3e:be:78:72:c8:f4.
Are you sure you want to continue connecting (yes/no)?
When you've done that, you get another warning that can be ignored:
Warning: Permanently added 'freenet1.afn.org,188.8.131.52' (RSA) to the list of known hosts.
Then you'll be prompted for your password.
Enter your AFN password, and you'll be logged on after a short period for credential check. After a brief message flash, you should then see the options menu.
Future log on sessions will usually skip the authentication warnings, though if the SSH service has been moved to another freenet machine, it will happen again for the new machine. Enjoy!