How do I had an underline?

Hi,

Thank you for contacting us.

If you are trying to add the underline to the label in your field, you can do it by adding the next CSS code in the Designer tool : 

#id{

 text-decoration:underline;

}

This guide will help you to find the field's ID : http://www.jotform.com/help/146-How-to-find-Field-IDs-Names 

And if you are trying to add a underline when using the Text, just follow the image below :

Hope this helps.

Feel free to contact us if you need further assistance.

Thanks.