The way those form fields appear on the signup form are set by your WordPress theme. They are standard form text inputs wrapped in paragraph tags, with labels for each field. The plugin does not define any separate CSS styles for the signup form fields. Check the CSS styles for your theme, and if you don’t like how it’s displaying, you will need to alter the CSS styles for text input fields. If you only want to target the specific text inputs of the signup form, each signup form field has an id that you can target with CSS. They are:
signup_firstname
signup_lastname
signup_email
signup_phone
signup_item
