How can I add a lead pixel on jot form and also a purchase/complete resignation pixel. This is for Facebook advertising

Unfortunately, it's not allowed to add any sort of code to the form, this is due to security reasons. 

If you need to add your own code, then you may need to get the form's source code instead, this guide will help you getting it: https://www.jotform.com/help/104-How-to-get-the-Full-Source-Code-of-your-Form