Log into the Google Cloud Console:

https://console.cloud.google.com/

Select your project that you’ll be working with, or create a new one.

Click on “Keys & Credentials”

Click on “Create credentials”

Now click on “OAuth client ID”

Now click on the Application Type dropdown and select “Web application”

Give your application a name. I traditionally use the name of the website such as “Frostline Works” when creating these.

When that is all done you’ll click on the create button

After you’ve clicked on the “Create” button you’ll get a popup when its successful. Close it because not all the information that we need is in there.

After you close that click on “Clients” on the left side navigation menu.

You’ll find the name of the client ID in the name column that you created a minute ago. Click on it.
In my case I created one called “Frostline Works 2”

On the “Client ID for Web application” screen you’ll find the items that I’ve selected in purple and blue.
Purple is the Client ID, blue is the Client secret.