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.
I strongly suggest creating a page for your subdomain then you can embed the form using the embed code listed here: https://www.jotform.com/help/67-Which-form-embed-code-should-I-use
I strongly advise using the iFrame embed code.
If what you would like to do is redirect your subdomain link to your JotForm form instead of embedding, that should be possible by following this guide: https://www.jotform.com/help/144-How-to-use-Custom-Domains-with-Jotform. However, it does NOT support SSL (HTTPS). I strongly suggest embedding the form instead.
I hope that helps.