How to open only external links in a new tab on Vintagio theme?

Store Design
1

I’m using Vintagio theme and I would like to open all external links in a new tab. I’ve searched and found solutions that open both internal and external links in new tabs but nothing for just external links.

I also came across this article which addresses the issue using the following code, but where exactly do I put this code?

Any assistance much appreciated.

{% assign externalLink = false %}

{% if link.url contains 'https' or link.url contains 'http' %}
  {% unless link.url contains shop.url or link.url contains shop.secure_url %}
    {% assign externalLink = true %}
  {% endunless %}
{% endif %}

<a href="{{ link.url }}" {% if externalLink %}target="_blank" rel="noopener"{% endif %}>
  {{ link.title }}
</a>