How to create pay button on submission form?

How PayPal knows what is my email address. I try to add pay button on the form and got this error message

We cannot process this transaction because there is a problem with the PayPal email address supplied by the seller. Please contact the seller to resolve the problem. If this payment is for an eBay listing, you can contact the seller via the "Ask Seller a Question" link on the listing page. When you have the correct email address, payment can be made at www.paypal.com.

I didn't publish this form yet, because of error.

I have checked your JotForm and see that there is no PayPal email address added in the payment wizard. Please update the payment wizard with your PayPal email address so that the payments should be working fine on your form. Please see the screencast below that can help you with updating your PayPal email address in the form by replacing 40.

Please get back to us if you need any further assistance. We will be happy to help.