It's easy to change the bank account for your loan payments. Just go to your Settings page (you can find the link in the menu below your name), and click Add an Account.
Enter your bank information to add your account. You can also choose to turn on AutoPay from your new bank account at this time.
If you don't see the Add an Account link on your Settings page, give Prosper Customer Support a call and an agent will be happy to help you out!