How do I choose which of my bank accounts a credit card payment goes into?

You can choose the bank or credit card account when you set up online payments, @cdsstudent25-gma.

Here’s how to set the Credit card or Bank transfer (ACH) when you turn on QuickBooks Payments:

1. Go to the Invoices menu and click on Create invoice.
2. On the New invoice page, scroll down to the button and click on Set up payments. 
3. Select the Activate payments link and follow the steps.
4. After you activate payments, select the Credit card or Bank transfer (ACH) toggle to turn on the options. 

Check this article for more information: Create invoices in QuickBooks Self-Employed.

Also, here's more information on how to add your income and expenses in QBSE manually: Manually add transactions in QuickBooks Self-Employed.

Let me know if there's anything that I can help you with setting up online payments. Take care and have a wonderful day!