You must already have a valid Google account in order to use the Google Calendar feature. You then have to authorize my application to access your calendars. Usually, authorization only needs to be done once.
It should be noted that you will need access to the internet in order to do this. Finally, if you have a software firewall installed, you may see pop-up windows asking for permission to access the internet. Please grant permission.
Click the Options menu and then select Google Calendar Options. If authorization is required then you will see this message:
Dismiss the pop-up message by clicking OK. It will now display the main Google Calendar Options dialogue:
As you can see, the calendar list is indeed empty. Now press the Authorise button (highlighted on the above screenshot). It will take you to your web-browser:
Select the account that you are using from the list presented. You might only have one account listed. Please click on it. This takes you to the confirmation page:
Now click the Allow button. If all has gone correctly you should see is a message that it worked:
Sometimes the browser displaying the notification automatically closes. But you should see it, albeit momentarily.
Meeting Schedule Assistant should now inform you that the authorization has completed. This might not immediately be obvious. But if you look at the screen, you should see that Meeting Schedule Assistant is flashing in the taskbar:
Click on Meeting Schedule Assistant and you should see this message:
Remember the message that was displayed in the web browser? It can now be closed down if it is still visible (close down either the browser or web-page). You should see that the calendar list is now populated:
It will only list calendars that you own (can write to). From now on you should not need to authenticate. The rest of the options are all explained in the Google Calendar help topic.
To revoke authorization at any point in the future all you need to do in this dialogue screen is press CTRL+R. You will need access to the internet and it will remove access from your Google account and reset the calendar list. You can also check the Google pages on this subject https://support.google.com/accounts/answer/3466521, which also provides a direct link to revoke access to applications.
If you get an error message when trying to revoke, then just try authenticating a second time, and then revoking.
This completes the overview of the authorization process and how you manually revoke access.