What is JotForm?
JotForm is a free online form builder which helps you create online forms without writing a single line of code. No sign-up required.
At JotForm, we want to make sure that you’re getting the online form builder help that you need. Our friendly customer support team is available 24/7.
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.
You can view the following guide on adding a custom domain for your form here: How-to-use-Custom-Domains-with-Jotform
Please feel free to contact us if you need further assistance.
but where is the setting in jot form to setup the domain
If you want to use custom domain to your form URL, you have to configure it on your domain panel or your website cpanel. That is where you need configure the mapping as seen on the guide. This isn't something to do on the Jotform side. :)
However, if you want to use just custom URL, follow this guide: http://www.jotform.com/help/261-How-to-create-a-Custom-URL-of-a-form
If you have further questions, let us know.