Before you can log into these systems, you need a kerberos password. If you set a password when you arrived, you should have already done this. If not, you can visit AVW 4120 to set your Kerberos password.
You must also change your kerberos password with the kpasswd command. See the man page for kpasswd for more details. kpasswd may be run from any department UNIX machine.
If kpasswd doesn't work immediately, try running kinit first.