Custom CSS Classes on Fields Add-On easily extends the functionality of Profile Builder by allowing you to add custom css classes for fields.
This addon is included in the main Profile Builder plugin. To activate the Custom CSS Classes on Fields Add-on navigate to the Add-ons page, locate it under the Free Add-ons sections and click Activate.
After you activate the add-on a new option will be available for your fields in Profile Builder -> Form Fields.
The following field types will have a “CSS Class” text input in which you can add your own CSS classes for that field.