How do I pass fields to an embedded form?

I need to pass a couple of form fields from one form to another, but the recipient form is embedded in an html page. What's required to make this happen?

You must be referring to the method described on our user guide: 

https://www.jotform.com/help/164-Pass-Value-to-Another-Form-with-URL-Encoding

Let us know if you need further assistance.