Need help creating an "Added to Cart" event for Shopify (Theme "VOGUE")

Hi! Im wondering if someone could please help me.

I am using Shopify’s “VOGUE” theme and can't seem to create the “added to cart” event for Klaviyo. I have been using this article in trying : https://help.klaviyo.com/hc/en-us/articles/115001396711

In this article, I use snippet 3 under the “theme.liquid” section (using class notation). Here is what shows up with I “inspect” my add to cart button on my website:

<input type="submit" class="button product-add-available pn-button-5a1rxhfa4yq" value="Add to cart">

Thus I hope I correctly assumed that I should use snippet 3 in the above article, using class notation.

This is what it looks like when I try to code it in:

{% if product %}

<script type="text/javascript">

var _learnq = _learnq || [];

  var classname = document.getElementsByClassName("button product-add-available pn-button-p3ysqtfmy99");

var addToCart = function() {

_learnq.push(['track', 'Added to Cart', item]);

}; for (var i = 0; i < classname.length; i++) {

classname[i].addEventListener('click', addToCart, false);

}

</script>

  {% endif %}

I still cannot seem to get it to work =(. Could someone please help me? Maybe it has something to do with my theme on Shopify. I would really appreciate it! 

Thank you in advance

Katarina