Alan,
If your console prompt is asking for a password, it must have already been put through the setup dialog by someone. If you don't have this password you'll need to do a password recovery.
In short while connected, reboot the switch (you can eject it from the Chassis and re-insert it). As the blade boots start pressing "Ctrl+]" (if that doesn't work try (Ctrl+R"). Eventually the switch will boot into the loader. From here you can boot the kickstart image and then assign a new admin password. Once saved you reboot the switch and let it fully boot this time. After this you should be able to login with the newly assigned password.
Full insturctions here: http://www.cisco.com/en/US/docs/switches/datacenter/sw/password_recovery/nx_os_pw.html
Regards,
Robert
