Hello Dani,

Welcome to the Klaviyo Community!

If you haven’t already, I would suggest taking a look at our helpful How to Create an Email Welcome Series Help Center article. The article also provide video walkthroughs that not only explains how a Welcome Series flow functions, but also some basic tutorial and guidances. 

Generally, a Welcome Series flow is triggered when a subscriber is added to a list that is linked to the flow. Oftentimes, it wouldn’t matter what signup form they were originating from. This means you could have a Klaviyo built pop up form present and a Shopify embed form present which would still be serving users the same Welcome Series Flow. 

Bear in mind that if you using a Shopify signup form, you’ll want to enable the Collect email subscribers settings in your Integration settings as well as include the below hidden input tag to your form's input group as mentioned in the Collect Email Subscribers subsection of the Guide to Integrating with Shopify Help Center article:

<input type="hidden" name="contacthtags]" value="newsletter">

In addition, if this was a form built on a third-party provider who didn’t have their own connection with Klaviyo, you’ll want to take a look at the How to Redirect Existing Signup Forms to Klaviyo Help Center article to find steps on how to set up a redirect to add users to a Klaviyo list. I would also recommend taking a look at some other Community post that discuss this topic further. I’ve included some below that have helped others!

I hope this helps!

David