Unlike older versions of Office that used product keys, Office 365 for Mac uses a .

If you purchased a physical or digital product key, go to setup.office.com and enter the key to link it to your Microsoft account.

Activating Office 365 on your Mac is essential to:

If you simply need to open and edit Office files, use (Pages, Numbers, Keynote) – free on all Macs. Or use LibreOffice (totally free and open source). Both can save files as .docx and .xlsx.