@dbj i don’t believe that is recommended. The intent is to use outlook office 365 email and calendar with SB. See https://support.smokeball.com/hc/en-us/articles/9818509298839-Using-Smokeball-with-Microsoft-365#h_01GF1A0YQHAHZ6M2PV7A92JWTQ. 
 

In theory you could find a way to sync google calendar to outlook and then sync outlook to SB. But, I suspect this would work very poorly and create errors. If you try it then let us know how it works out for you. 

@dbj Jonathan is correct again!  We do not have an option to sync directly to Google Calendar.  You can only sync with an Outlook Calendar. We do not recommend have both Smokeball and Google Calendar synced to Outlook at the same time.  This causes many issues and duplicate events.