The Permutive MailChimp integration allows you to move MailChimp users in and out of interest groups. We will run through how to create a reaction adding users to MailChimp groups first.
Go to the Reactions section of the dashboard, and then click Create Reaction.
In MailChimp, you need to find the ID of the list your users are in MailChimp. You can find this under Settings > List Names and Defaults on the list page
Put this List ID into the relevant field in the Reaction setup. Next, type the name of the Interest Group you want users to be added to in the field.
Pick the Segment you wish this reaction to be tied to, and pick On Entry. Click Create and you're done.
The process of removing users from MailChimp segments is the same, you just need to change the reaction to On Exit and Remove the following MailChimp interest from this user.