This process should work with any version of Thunderbird (newer than 52.0) running on any platform.
The first thing you have to do is download Provider for Google to allow bidirectional access to Google Calendar.
Open your web internet tool and navigate to theProvider for Google Calendar web page.
Save the file to your Downloadsdirectory.
Open Thunderbird and clickMenu(three lines)Add-ons and Themes.
Click theSettings(gear icon) drop-down, and then clickInstall Add-on From File.
Navigate to the Downloads directory and snag the newly downloaded file.
SelectAddto confirm that you want to add Provider for Google Calendar.
The Provider for Google Calendar extension is now enabled.
grab the extension to see its details or to set preferences and permissions.
On your Thunderbird inbox page, select theCalendaricon.
SelectNew Calendar(plus sign).
SelectGoogle Calendar, then clickNext.
input your email address and selectFind Calendars.
drop your Google account password and clickSign In.
SelectAllowto give Provider for Google Calendar permission to access your Google account.
Your Google Calendar or calendars are now available to view on your Thunderbird Calendar page.
Select a calendar to view its contents.
