As of March 21st 2019, the Mailchimp for Shopify integration has been removed from the Shopify Marketplace.
View Mailchimp's official statement
Learn more about Mailchimp's changes to their integration with Shopify, instructions to sync your contact lists, and manual workarounds for marketing features.
The Newsletter form action URL setting of the Turbo theme will continue to function for adding email address submissions to a list on Mailchimp.
- From your Shopify Admin, click Online Store > Themes > Customize to open the Theme Editor.
- From the Theme Editor click into Theme Settings > Newsletter.
- Input your Newsletter Form Action URL.
Finding your MailChimp Form Action URL
- Login to your MailChimp account.
- You will need to have a List in order to obtain your Form Action URL. You can create a new list by clicking the Create a List button from your MailChimp dashboard. Once you have created a list your screen will display all the lists you've created:
- Click the List you wish to connect to your Shopify account.
- From the chosen List, click Signup Forms > Embedded forms.
- Scroll down until you see the heading "Copy/paste onto your site".
- You can find your URL in this codes section, highlighted here:
Note: Your code will appear slightly different.