How to Add a Mailchimp E-mail App to a Facebook Page
Configure the e-mail app connection.
Select the Facebook Page where you’d like to add the e-mail app; then select the List to Use or your Mailchimp e-mail list. Choose Yes under Use Signup Form Tab because that adds the actual app to your Page. Choose your Form Theme or design from Mailchimp. You can change the Tab Label from Email Signup to another short action statement if you’d like. Click Save.