This is a great question! If you have imported your customers from MailChimp to your Shopify store, you should be able to see the list of customers by navigating to theCustomer sectionof the Shopify admin. In order to mark all of your customers toaccept marketing, you will need to select the desired customers accounts, or select all by using the checkbox located towards the top. I took a screenshot from my test store to show you the section I am referring to:
Once you selectEdit customers, you will be taken to the customer bulk editor.You can then selectadd tag > accepts marketingif the tag is not added towards the top of the page.
After the tag has been applied, you can then check the boxes that appear beside your customer's name to allow them to accept marketing emails.
Let me know if you have any additional questions.
Ollie | Social Care @ Shopify - Was my reply helpful? Click Like to let me know! - Was your question answered? Mark it as an Accepted Solution - To learn more visit the Shopify Help Center or the Shopify Blog