With the MailChimp API, to add a member to a list with a specific interest group, you need both that list\'s ID and the interest group\'s ID.
To get both those IDs, you
You can use the Playgrounds in the Mailchimp Developer site located at developer.mailchimp.com
The Playground is a UI into the API and you can drill down using the Subresources into -> lists -> interest-categories -> interests.
Then choose the Response view and it will show the payload of the response that contains the id's you are looking for.