I'm trying to make the "Input Table" column width wider so the dropdown looks better.

Hello!

I'm trying to make the "input Table" column width wider so the dropdown looks better, but it says it can only be done with a CSS code and I don't see the CSS option on my Form Builder

It looks like you are referring to this form https://www.jotform.com/form/211015499499061. Unfortunately, CSS is only available in Classic layout. To change your form layout, please follow this guide https://www.jotform.com/help/493-how-to-change-the-form-layout.