Display field titles as placeholder text on Mailchimp subscribe widget form

Hi,

I would like to change how the mailchimp widget displays.

Instead of having the field title displayed above the fields I would like to display them inside the text and email fields. (as placeholder text that will be deleted as a user enters their details.)

This applies to first name, last name and email fields.

Can you please recommend the best way to do this.

Thanks
Chris