Here are the steps to follow:
Add the following tags to the end of your Destionation URL:
?kendall_source=pinterest&kendall_adid={adid}
For example: if the Pinterest ad in question is meant to direct prospective customers to *https://yoursite.com/product*, then the following text should appear in the Destination URL text field:
<https://yoursite.com/product?kendall_source=pinterest&kendall_adid={adid}>