Go to Google Cloud Console | Create Project, and create a new project.

Search for "Oauth console screen" in the search bar, and click on the first result.

Click on the "GET STARTED" button.

Enter the App Information section.

Select the External option.

Input the Contact Information section.

Check the Google API Services User Data Policy and click on the CREATE button.

Now search for "Credentials" in the search bar, and click on the first result.

Click on the Create Credentials button, and select the OAuth client ID option.

Follow the Screen Shot below to create the OAuth client ID.

Now you can see the OAuth client ID and client secret! Please save them in a safe place.