Mailchimp Integration is entirely automatic. Just authorize Accumula to connect to Mailchimp and Accumula will send each Customer who has an email address in Point of Sale to Mailchimp. This will include any Customers included on orders received from Shopify, Magento, or your other integrations, as well.
In addition to sending and updating this info, Channels can automatically create segments based on the Birthday Month and Customer Category. These segments allow you to easily target your Mailchimp Campaigns.
The switches in the Channels UI control whether these segments are created or not.
If you have Premium Plan or above, you have the option to send Customer Purchase History to Mailchimp. Accumula Support can enable Purchase History Integration for you at your request. If you are already using Mailchimp's direct integration for Shopify or Magento, you can exclude online sales to prevent double recognition using the "Do Not Sync Ecommerce Orders setting.