artisana on "[Plugin: MailChimp List Subscribe Form] Adding Birthday field for Mailchimp Subscribe Plugin/Widget"

Hello!
I am looking to add a simple birthday (mm/dd) field into my Mailchimp subscribe plugin on this site.

Can anyone help direct me as to how I can add this?

Thank you in advance for your replies!

Cheers,
Ana

http://wordpress.org/plugins/mailchimp/