Sign into your Facebook account.
Click "Account Settings" under "Account" on the top right of the page.
Click the "Payments" tab.
Click "Remove" next to your PayPal payment information.
Now if you are trying to Cancel your PayPal account or Credit Card under an Advertisement for your Facebook Business page, then that's a little more detailed.
First, you have to cancel all running ads first, before you can cancel your account on Facebook. Now, if some reason that doesn't work, then you need to go to the website attached.