How to add Google login and registration to WordPress
Navigate to https://developers.google.com/identity/sign-in/web/sign-in and click the "Configure a project" button. A new window will open which will guide you through the setup of a new project. From the dropdown then click "Create a new project" and type the name of the project.
In the next screen you'll be asked to enter the name that will be displayed to your users when they'll try to login or register via Google. Enter the name and press the next button.
Now that your client has been created, you'll be given the Client ID and the Client secret keys.
Login into your WordPress dashboard and navigate to Settings → Posterno → Accounts → Social login and locate the settings "Google Client ID" and "Google Client Secret" and type in the credentials given to you by Google and save the settings.
From the previous popup, click on the "API Console" link at the bottom of the popup, in the new page, click the "Enable apis and services" button.
Search for "identity" and then click on "Identity toolkit API" and then click on "Enable".
Click on "Credentials" in the right side of the screen then select "Oauth client" and you should see a page like this:
under the "Authorized redirect URIs" enter your website url followed by