Connect Mailchimp to Shopify
"Log in to your Mailchimp account, click your profile name, and choose Connected Sites.
Click Shopify in the list of logos and click Connect. Click Shopify in the list of logos and click Connect. On the Shopify installation screen, click Add app .Enter the domain name for your Shopify store, and click Log in. Enter your Shopify login credentials, then click Log in again. Click Connect existing account. Choose a Mailchimp list to connect to your store, and click Connect List."