Make sure you do not have any other versions of Office installed on your computer before installing Office 365. You must have an active University of Illinois NetID to successfully complete these steps.

Link for Office 365 installation: https://portal.office.com.

Webstore written instructions for installing Office 365 can be found at the link below.
http://dl.webstore.illinois.edu/docs/ii/office365uiuc.html#mac