Open up your Google calendar on your pc
Down the left hand side click on the arrow to the right of Other Calendars
Click on Add a friend’s calendar
Type in the Union email address firstname.lastname@example.org
and click Add
A new window appears and just click on Send Request.
Once I get the Request and sort things out my end you will receive an email.
Click on link in email. It should open up your Google Calendar settings page
Click on Add Person in grey line across middle of screen
Click on SAVE
Hope that helps. You can always remove the Union calendar if you don't like it.