How to get a Google OAuth 2 token for API testing

I am trying to build a simple node API that uses Google OAuth 2.0 to authenticate endpoints, and I am trying to test it by making calls with Postman, but I cannot figure out how to get an OAuth token for my google account to use when calling the API. I tried using the OAuth feature in Postman but could not get it configured properly.

How to either obtain a token I can use or properly use Postman/any other utility to do this testing?

Here's how you can use Google's Sign-In button template to initialize the login & grant of permissions process (provided the project is set up in the Google Developer Console):

<meta name="google-signin-client_id" content="{{ OAUTH2_CLIENT_ID }}">

<script src="https://apis.google.com/js/platform.js?onload=onLoad" async defer></script>

<div id="google-signin-button"
     class="g-signin2"
     data-width="170"
     data-height="30"
     data-onsuccess="onSignIn"
     data-onfailure="onSignInFailure">
</div>

function onSignIn(googleUser) {
    var profile = googleUser.getBasicProfile();
    var idToken = googleUser.getAuthResponse().id_token;//this is your token
}