How do I sync a Salesforce Campaign to Mailchimp?

You can sync Salesforce Campaign members to Mailchimp via the Data Wizard. Choose Salesforce Campaigns as the data source on the first step of the wizard. To locate a specific campaign, search for it by name. We will also list several recently modified records for quicker access. 

You can then filter which Campaign Members are included by their member status if needed. 

The fields available for mapping are those on the Campaign Member object. To include contact or lead fields not already included on campaign members by Salesforce, you will need to create a formula on the campaign member object. Or you can consider a report type that combines the fields you need and use a report-based data wizard instead. 

Guide: Data Wizard