To ssh to your mark 1, assuming your system supports mdns/bonjour, say:
The first time you do so you'll see the key fingerprint for your mark 1, and it will ask you to confirm it:
Are you sure you want to continue connecting (yes/no)?
yes, and it will remember that for future reference, and check when re-connecting.
As noted above, the password is initially just "
mycroft". You should immediately change it by running this and following the prompts to choose a strong new key. 'Cause you don't want others hacking into your AI agent.....