To subscribe to your Google Calendar, you’ll first need to get the iCal link to your calendar. In Google Calendar, go to Settings \ Calendars and then click on your calendar in the list.
You should see a “Private Address” section:
Right click on the ICAL link, and choose Copy Shortcut to copy the link to the clipboard.
Now open Windows Calendar, and click the Subscribe buttton on the toolbar:
Paste the URL into the textbox, and hit the Next button:
After what seems like far too long, you’ll see the next screen:
The key thing that you’ll want to choose on this screen is the Update interval, which will keep the calendar automatically sync’d up. I also chose a friendlier name.
That’s all there is to it. Notice the blue appointments are the ones that came from Google Calendar: