1) In the OSX interface, go to the Finder, then go to the Go menu, and choose Connect to Server.  For the Server name enter…

smb://<servername>.andrew.ad.cmu.edu/<sharename>

For example...

smb://randon.andrew.ad.cmu.edu/etc

2) This will popup a login box.  The first field should be ANDREW, the second field should be your Andrew user ID, and the third should be the Andrew Kerberos (email/WebISO) Password.