I can share some information about setting up online payments.
Fiat is right. You need to have a free invoicing app to offer PayPal and/or Stripe as payment options and utilize a connector to mirror data back into your QBO account.
In addition to that, you may be able to achieve this through the "Message on Invoice" or "Memo" or "Description" columns when creating your invoice, or through the use of a Custom Form Style, where the link is added onto one of the content sections, or messages (memo/email/description).
Sometimes, these companies will have a 3rd party app developed to work with QuickBooks, you can search for any 3rd party apps here - https://apps.intuit.com/
Feel free to post again here if you have further concerns in processing invoice payments. I'm always around to help. Take care always!