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.
If I am not mistaken, you're referring to this form? https://www.jotform.com/42211013452133
First, you have to upload your image to your server or to any image hosting services like www.tinypic.com so you can take the image URL and update the one on your form.
To change the image on your form, you have to edit the HTML content. Click the image so you can open its properties by clicking the image icon found on the formatting toolbar below.
See these visual guides:
If you need further assistance, let us know here.