Hi Rita,

Check this step by step with some screenshots:

1. Go to the Developers Console Credentials page here.

a. From the project drop-down, select your project or create a new one.

b. On the Credentials page, select Create credentials drop-down and then select OAuth client ID.

It is your first time; you'll need to add the OAuth consent:

c. On the Application type, choose Web Application.

d. Give a name to the project, and give an authorized redirect URIs.ii. Example: https://<hostname>/GoogleCalendar/OAuthCalendar.aspx

e. Hit Create.

2. Note the credentials somewhere, or download them to your computer. 

3. Then, go to Configuration ( URL: just need to change the hostname)

a. Fill in all the attributes.

b. Save the configuration.

4. That's it! You can now go to the Calendars page and see the results.