How to Design Text Field Inputs in Gravity Forms without Coding. https://wpmonks.com/blog/how-to-style-text-fields-of-gravity-forms
Here is the complete step by step tutorial to change the design and styling of text box inputs using Styles and Layouts for Gravity Forms plugin.
To manually add CSS codes for text inputs you can follow the above link.
Tags: How to Design Text Field Inputs in Gravity Forms without Coding, styles and layouts, gravity forms css, gravity forms design, text inputs css, css tutorial