I would like to make the phone number larger.
I would like to make the phone number larger.
If you want to change any of the styling you need to do so using CSS. You would write CSS to target and style specific form elements by adding CSS to your themes stylesheet to target and style whatever it is you want to customize.
Here is some documentation that discusses how to target specific form elements using CSS:
http://www.gravityhelp.com/documentation/page/CSS_Targeting_Samples