How can I block an IP Address to prevent multiple submissions from one formuser?

how do i block an IP address from someone filling out the form multiple times.

In order to block an ip address to prevent a formuser from filling in your form multiple times you would need to change the submission type for unique submissions.

Please see https://www.jotform.com/help/64-How-to-Set-Unique-Submissions-on-a-Form for details.