How do I test Paypal integration?

I followed instruction as provided and now have registration set up.

1. How do I test the functions?

2. How do I allow volunteers to register and waive their costs?

You have to preview the form. If you want to test an actual payment, you have to submit and pay with your other card that is not linked to Paypal. You can also test it up by enabling sandbox mode. 

https://www.jotform.com/help/390-How-to-Test-Paypal-Payment-Form

With Paypal, you as the seller will pay for the charges. That's Paypal's terms. You have no option in Paypal to charge users with the fees. 

Let us know if you need further assistance.