How do I install Sphere on the Mac when I get the error "Sphere Setup can't be opened because it is from an unidentified developer"?

If you see this error when running the Sphere plug-in Mac installer:

Sphere-Installer-Cant-Be-Opened

 

You can fix this problem by going into the Security & Privacy settings in the System Preferences, and clicking on "Open Anyway" for the TownsendLabsSphere-MacSetup.pkg file.

Sphere-Installer-Was-Blocked