this is in the google Home help site: "
- Reminders. Note: To hear reminders, they must already be set in the Google app or Google Calendar. You can't set Reminders in the Google Home app or using your voice. "
so seems that you can hear the existing calendar entries but not enter anything new the Home. I hope that is fixed soon. However, it seems that you can add entries to Google Keep lists. wonder why Keep and not the Calendar...?
Google Home Support | Google Home Setup | Google Home Help