It's easy. Right there in the File menu near the Save command is Revert To, which leads to a submenu with Previous Save and Browse All Versions... options. The latter uses the slick Time Machine UI (http://support.apple.com/kb/ht4753).

Except, per my other comment, Microsoft doesn't bother writing Mac software that works like Mac software. It's kind of like running Java desktop software (actually worse)... neither native feel nor integrated with the OS like other Mac apps.