Please review the plugin documentation from below specified links if you still can't find the answer.

User Documentation

•  Creating a Form
•  Embedding a Form
•  Reviewing Form Submissions
•  Configuring Confirmations
•  Configuring Notifications

Developer Documentation

•  Getting Started with the Gravity Forms API
•  API Functions
•  Web API
•  Add-On Framework
•  GFAddOn

Designer Documentation

•  CSS Selectors
•  CSS Targeting Examples
•  CSS Ready Classes
•  gform_field_css_class
•  gform_noconflict_styles