Tip: If you see an error that says the Microsoft_Office_2016_Installer.pkg can't be opened because it is from an unidentified developer, wait 10 seconds and then try double-clicking the installer package again. Once the download has completed, open Finder, go to Downloads, and double-click Microsoft_Office_2016_Installer.pkg.On the Office page page, under Install Office 2016 for Mac, select Install to begin downloading the installer package. Sign in with your work or school account at.