Thank you for reaching out to Constant Contact API Developer Support. My team is here to assist outside software developers with questions about building into Constant Contact's API.
Based on what you supplied it looks like you're using the Constant Contact Wordpress Sign-Up Form. To adjust padding or add custom classes you can follow the steps below but we can't guarantee the custom CSS will format the form accordingly. Because you'll be overriding the default styling and using your own custom CSS we won't be able to offer further assistance on overriding the styles. You can however use this approach to attempt your desired results.
Hover over Contact Form
Click on "All Forms"
Click on the Form name you wish to edit
Go to the "Input Design" section
Use the Custom Classes section to add some custom CSS classes.
Please reply directly to this post if you have any other questions!
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