Hello there, beardshooting.
I'm here to share more information on how payment processing works in QuickBooks Self-Employed.
QuickBooks Self-Employed is a standalone product. Thus, we're unable to integrate another app into the program. To ensure you can process payments, I'd suggest reaching out to Authorize.net support. They'll be able to guide you through the process.
Feel free to browse this link here if you need help with other tasks in QBSE. It has our general topics with articles.
Please know that I'm just a reply away if you need any further assistance managing your invoices.