How does someone complete their submission by making a payment?

Ihave submissions that have checked the box to say they'll make a payment through paypal, but didn't pay before submitting the form. How do they go back to complete an incomplete payment?

Thanks

Sophie

I understand that you want to receive the payment for the incomplete payments. Unfortunately, completing the submissions from the incomplete payment submissions doesn't process the payments. It is required for the user to submit the form again to complete the payment. Please refer to the Incomplete payment submissions FAQ for more information.

https://www.jotform.com/help/272-Paypal-Incomplete-Payments-FAQ

Thank you!