In order to use Calendar Sync for Jira with Google Calendar, follow the steps below.
In Jira, click your profile icon in the top right-hand corner of the screen. A menu will appear. Click My calendars.
The page shows all the feeds and calendars available to you.
Copy calendar URL to clipboard using the Copy to clipboard button, or directly from the text field.
In Google Calendar, expand the dropdown for Other calendars and select Add by URL.
Paste the address from clipboard and click Add Calendar. An example URL is shown here; your URL will be much different.
After a short while the calendar will appear under Other calendars and the events will be visible in the calendar grid.
According to its documentation, Google Calendar will automatically refresh the calendar several times a day. It may take up to 12 hours until a change in Jira is reflected in Google Calendar. This delay is entirely under control of Google calendar; Calendar Sync for Jira provides updated data within 5 minutes. User cannot perform the refresh manually.