Tracking a mailchimp submission in Google Analytics

I am trying to set up some advanced reporting in my Google Analytics (it’s a mailing list signup that also gives the person who completes the signup a download link) and I wanted to track the form completion in Google Analytics.

Is there anywhere I can add some tracking code to make this happen and if so, what’s the code? I know that if it was a Contact Form 7 form completion, I could add the following to the head.

<script>
document.addEventListener( 'wpcf7mailsent', function( event ) {
    ga('send', 'event', 'Contact Form Name In Here, 'submit');
}, false );
</script>