To begin with,

To begin, obtain OAuth 2.0 client credentials from the Google API Console

Got this from below:

Google Documentation https://developers.google.com/identity/protocols/oauth2

Configuration

https://console.developers.google.com/apis/credentials

Then

  • your client application requests an access token from the Google Authorization Server,
  • extracts a token from the response, and
  • sends the token to the Google API that you want to access.

Same steps in detail:

given here: https://developers.google.com/identity/protocols/oauth2

New Project:

on same page, asks for Authorized redirect URI

As per https://next-auth.js.org/providers/google

Configuration
https://console.developers.google.com/apis/credentials

The "Authorized redirect URIs" used when creating the credentials must include your full domain and end in the callback path. For example;

For production: https://{YOUR_DOMAIN}/api/auth/callback/google
For development: http://localhost:3000/api/auth/callback/google

Going to use

http://localhost:3000/api/auth/callback/google