Add to list based on Product ?

Hi there, I think what I need is similar to this post: https://www.ads-software.com/support/topic/only-sign-up-to-mc-when-order-completed-and-product_id?replies=3

I am just wondering if you could explain that in laymen’s terms as I’m not so familiar with php. I would be forever grateful! Thanks ??

https://www.ads-software.com/plugins/woocommerce-mailchimp/