Grab your ProveSource snippet code.
Follow the instructions mentioned in this blog post by Unbounce on how to add custom JS code to your landing page: Using Custom JavaScript and CSS on Your Landing Page
Create a new Stream or Conversions notification.
Track your Unbounce leads by configuring a webhook: Unbounce - Using a Webhook or use the "Form Submission" tracking option to let ProveSource automatically track form submissions on your landing page.