Adding through ServiceBridge
The easiest way to add to and edit your current payment methods is to go to your Company Settings and scroll down the Accounting Section.  Under Accounting there is a section called Payment Methods.  Scroll down and click +Add new.

Name the new Payment Method and make sure to check the box 'This is a credit card' if if this applies and click Save.  Your new payment method has been added.

Adding through QuickBooks
You can also add and import new payment methods directly from QuickBooks Online.  Follow these instructions:

4. On the next screen, you will want to click on "Payment Methods"

5. To add a new payment method, click "New"

6. Fill out the "New Payment Method" form. You will need to add a "Name" and decide if this new payment method should require inputs for a credit card. If it should, check the box called "This is a credit card".
7. Click Save.
8. Now, you will need to go into your ServiceBridge account and force synchronization between ServiceBridge and QuickBooks Online. When you login into your ServiceBridge account, navigate to your name in the upper right-hand corner and click on it.
9. Click on Company

10. Scroll down to the section called QuickBooks
11. Click Synchronize

Once all these steps have been completed, you should see your payment method in ServiceBridge.