I can't figure out how to integrate paypal payment submission into my form

You can easily integrate your form with Paypal using our Form Builder. Please refer to these guides:

How-to-Integrate-Form-with-Paypal

Order-Form-Types

Setting-Up-Your-First-Order-Form

Difference-Between-PayPal-and-PayPal-Pro

Hope that helps. If you have any questions, let us know. Thank you.