Hi Matthew,
I do not have a Mac and am writing from my experiences with the Windows version. That version is similar, but the two are not the same. While I've used Word on a Mac, that was a long time ago. Nevertheless, I hope that I can be of some help.
You need to find the Page Setup dialog. Try the layout tab.
I hope this information helps. Please let me know if you have any more questions or require further help.
Regards