To activate the Google Social Login module you have to set the Google Client ID and Client Secret Key under 'Administrator - Settings - Users - Google Login Settings'.
These credentials can be obtained at https://console.developers.google.com
Click the 'My Project' dropdown that appears in the top menu to the right of the Google APIs logo. This will open a popup. Click the 'New Project' link in the top-right corner of the popup. On the 'New Project' page set your 'Project Name' and click the 'Create' button. Now click the top menu 'My Project' dropdown and select your recently created project from the list.
Click 'Credentials' link in the left menu block. Click 'Create Credentials' button and select 'OAuth Client ID'. On the 'Application Type' step select 'Web Application' option. Now set the internal client name of your OAuth 2.0 client. The 'Authorized redirect URIs' must include the following path: https://www.example.com/account/callback/google Click 'Create'. Your Client ID and Client Secret will appear in the popup.