For MacOS 10.8 and later, download and install the 64-bit version: MacOS-CommunicatorInstaller-x.xx-64.dmg
For MacOS 10.7 and earlier, download and install the 32-bit version: MacOS-CommunicatorInstaller-x.xx-32.dmg

You may receive a security warning when first running the application. This is because the Communicator
app is not signed nor downloaded from the Apple App Store. If this happens, enter the "Security and Privacy" 
settings of "System Preferences". In the "General" tab, you can override this warning.