Hi @Brutal Claire, 

At this time, Klaviyo doesn't have a pre-built Squarespace integration, but you can add a Custom eCommerce Integration using our API Guide and Actual API References. Alternatively, you could use Zapier to create this integration: https://zapier.com/apps/klaviyo/integrations/squarespace/23249/create-klaviyo-subscribers-from-new-squarespace-form-submissions

Specifically for your question, you can add a pop-up to your Squarespace site by using our new pop-up forms. You can get details on how to Install the Signup Form Code Snippet here.
This guide walks through installing a code snippet in the header of your site that allows you to publish signup forms from your Klaviyo account to your site. This is a one-time installation that updates automatically when you add new forms or edit existing forms within the Signup Forms tab of your account.

This guide walks you through how to use our Signup Form Builder.

Hope this is helpful! 
-Cass. 

Hello,

These instructions do not help with adding a Klaviyo pop up to a squarespace website from what I can tell.

1. I have added the zapier integration but that is only sending profiles to klaviyo that are entered in the onsite email collection.  
2. I have added the code snippet provided to the SquareSpace CSS area and when I run the test on Klaviyo to see if it’s installed properly, it says that it hasn’t
3. I have reached out to klaviyo customer support and they tell me to reach out to squarespace. 

Hey @LealynPapaya,

Thank you so much for reaching out to the Klaviyo Community for help with this!

Have you reached out to squarespace like support asked? As a community we absolutely want to make sure the help you want and need are easily accessible. When it comes to custom integrations please reach out to one of our Klaviyo Partners or your internal IT team for continued help with your signup forms on squarespace. 

Han anyone actually been able to make this work? I certainly haven’t, nor can I find ANYONE on the web who has, or who can explain how it’s done with Squarespace specifically.