Hey Edwin,
A segment is something that is done automatically inside your MailChimp.com list/campaign. However, you can add the users to a specific interest group within your list. To do this, first, add the interest group to your form and then replace the type from “checkbox” to hidden.
If you are not sure how to do this, please follow these steps:
1) Create Interest group in your MailChimp list
2) Go to “MailChimp for WP” menu in your WordPress admin and click on the “Renew MailChimp Lists” button. This will pull details of the new field.
3) Go to “MailChimp for WP > Forms” and add the interest group to your form.
Copy the code and share with us here along with details of which interest group you want the user to be added to. We will then modify the code and share it with you.