How can I add custom css?

I've built a form using JotForm and it all looks amazing on the desktop. 

However, there are a couple of adjustments that I'd like to make to the mobile version of it. 

None of them can be made via the jotform settings. 

I read the JotForm guides and saw that there is a custom "CSS" field. 

However, I can not seem to find it. 

Please advise how I can enable it. Is it on the higher plans only?

It looks like you are using the CARD Forms layout. Please note that CSS injection is not allowed in CARD Forms. If you want to customize the form using custom CSS code then you need to use CLASSIC form layout.