I want to add a user

Unfortunately, it is not possible to add another user in account. Please note that one account can only have one user. If you want to add multiple users in account, it is only possible to Enterprise plan.

Alternatively, you can also use "Form Collaboration" to let other user edit your forms. You can also add reports in form to allow access to your form's submissions. The following guide should help you:

Form collaboration: https://www.jotform.com/help/419-Understanding-Form-Collaboration

Add reports: https://www.jotform.com/help/326-How-to-Create-Form-Reports-in-JotForm

Hope this helps.

Do get back to us if you have any questions.