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.
We don't have the facility to allow users to login to jotform and exclusively fill in forms.
To optimally achieve your desired objective I would recommend embedding the required forms in your website, the setting an interface that will require the users to login in order to access these forms. This will make it easier to manage if the forms are many in number and you require a one time login.