JotForm is a free online form builder which helps you create online forms without writing a single line of code. No sign-up required.
We believe that if one user has a question, there could be more users who may have the same question. This is why many of our support forum threads are public and available to be searched and viewed. If you’d like help immediately, feel free to search for a similar question, or submit your question or concern.
I can only assume this is the form https://www.jotform.com/61515406385657 (let us know if its not).
And youd did not mention which field.. You can use the Size property of a Textbox field to change its width.
If you meant something more specific, you can do it via the CSS editor using the Form Designer.
Hope this help. Let us know if you need further assistance.