First, to actually try to help, could you link to the page with the instructions you're trying to follow?
Second, if you've got a mac laptop, why are you messing with ubunto? Do you not have OS X? The new macs are inherently unix underneath, and you can access their unix-ness by opening the Terminal app (in Applications under Utilities).
Third, why not just download the mac dmg? That's what I did on my mac laptop:
http://libprs500.kovidgoyal.net/download_osx