If a dialog box appears asking you to Open or Save the Event, click Open
Or, if you see the message: To help protect your security, Internet Explorer blocked this site from downloading files to your computer. Click here for options...
Click on the message and select Download File...
When the appointment box appears, select 'Save and Close'.
The event will be added to your Outlook Calendar.
This option is only available using the Windows Outlook client.
If not prompted, click on the the following link: Download Event.