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.
Upon checking your form, it appears that you have already centered the image that you are using as a header.
To center elements of the Text field that you are using, you can simply click on the Edit HTML, then click on the image (1), click on the icon that centers text (2), and then Complete (3) to save it.
Please let us know if I misunderstood your question, or if you have any other questions, we will be happy to help.