Is it possible to have the user enter an amount in a field and make the payment via Paypal? Below is the setup of the form.

Do I use "PayPal IPN" or "PayPal Redirect"?
Where do I put the one I need to use?
Thank you in advance!

Do I use "PayPal IPN" or "PayPal Redirect"?
Where do I put the one I need to use?
Thank you in advance!