The higlighted fields need to be filledup for successful Postman setup.

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Callback URL: https://oauth.pstmn.io/v1/callback  
Auth URL: https://accounts.google.com/o/oauth2/v2/auth
Access Token URL: https://oauth2.googleapis.com/token  
Client ID: This is OAuth2 client ID from Google Cloud Console  
Client Secret: OAuth2 client secret  
Scope: https://www.googleapis.com/auth/calendar (For Google Calendar. All Google Api scopes can be found here

Google Api scopes: https://developers.google.com/identity/protocols/oauth2/scopes

In Google Console, there is a 3 step process:


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Step 1: Create OAuth2 credentials

Step 2: Enable API, for example: Google Docs
Step 3: Add Scope to OAuth Consent Screen