Hi @Hopeyouhappyy and welcome to the PBC!
I'm assuming you are talking about the Pinterest Tag that helps track visitors to your website and other stats.
To install the Pinterest Tag to your website, the best way is to follow these instructions: https://help.pinterest.com/en/business/article/install-the-pinterest-tag
They may vary a little depending on your website.
In case you are talking about the HTML code that allows you to claim your website, please check this: https://help.pinterest.com/en/business/article/claim-your-website
I hope this helps.
Pinterest Specialist & Educator