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 you are talking about protecting your forms on JotForm, they already are since you are logging in with your username and password. So if you're not sharing them they are visible only to you.
On the other hand you can always create some log in screen that you will use to access your public form. But you can not do that on the form itself since the form is not login based form and it will be considered as potential phishing.
Please let me know if this answers your questions or if you have more.