Since MailChimp and Shopify are no longer together, MailChimp app is unavailable on the Shopify app store, however, if you have a MailChimp web account, you can still use it for email newsletter popup on Promotion Popup.
To use the newsletter popup, you need to find a MailChimp Form Action URL, please follow these steps to do it:
1. Log in to your MailChimp account
2. Click Create button on top of the page
3. Scroll to the bottom and click Sign up form
4. Select Embedded form, choose your list and click Begin
5. This is the interface of Embedded form section, scroll till you see a box that contains script code.
6. Find a line starting with "<form action=" in the script and copy the URL follows:
7. Open Promotion popup app and paste that URL in MailChimp form action URL box.
If you need any support, send an email to firstname.lastname@example.org