First of all, go to Google Cloud Console and create a new project.
Chose a name for your project and click on Create button.
Then, go to OAuth consent screen, chose external user type and click on Create button.
Fill out Application name, User support email and Developer email address and click on Save and continue button 3 times and finally click on Back to dashboard button.
And click on Publish app button.
Then, we need to allow Google Calendar API to access your google account. Select Library tab.
Search for Google Calendar API and select it.
After that, click on Enable button.
Now, you can generate your credentials.json file. Select Credentials tab and click on Create credentials button and choose OAuth client ID.
Select Desktop app as Application type, fill out Application name and click on Create button.
Then, download your generated credentials file.
