First you need to go into MailChimp and ensure that your list is set up correctly, including the appropriate Merge fields related to the different kinds of records - constituent or relationship.
Then you need to go into your settings in the Chimpegration Classic plugin, under the Lists tab and pick up the right settings for your list.
Then you need to ensure that you have one organisation relationship set up as the person to contact for each and every organisation you want to reach out to.
Then you need to create a query using the following criteria and output.
You should then get the following results - save the query and use the plugin as usual to export that new query.
Just make sure to select the option at the bottom when doing an export to notify Chimpegration Classic that you are about to export a relationship.
Please do get in touch with our support team should you have any further question(s).