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.
Have you checked our guide here: http://www.jotform.com/help/37-Adding-Form-to-Squarespace
If the form is cut off, you might need to adjust the height attribute of the iFrame.
Here is an example, make sure that the height attribute matches the height of your form.
Let us know if that works.