Hi there, @AGNES1408. I'm here to share some information about adding a logo to QuickBooks Online (QBO). Follow along below to get this done right away. 

In QBO, once you add a company logo on the Accounts and settings page, this will also appear when you print the credit note and statement of account. Let me guide you on how:

1. In your QBO company, go to the Gear icon and select Accounts and settings.
2. Next, click the Company tab and select the Pencil icon.
3. From there, select the plus button in the Company logo section to add a logo. I also suggest checking the criteria needed to ensure you'll be able to successfully upload one.
4. Once done, select Save and click Done. 
5. After that, go ahead and create a credit note and statement of account.
6. To check how the logo shows in the credit note, simply select the Print or Preview button located at the bottom left part of the screen after you finished entering the needed details.
7. To see how it will be displayed in the statement of account, just click the Print or Preview option located at the bottom part of the screen.

On the other hand, you can only upload logos for specific sales form templates such as the invoices, estimates, or sales receipts. For reference, feel free to visit this article: Add, customise, or remove logos on sales forms.

Additionally, I've attached this helpful resource that you can access for guidance in managing your customers in QBO: Add and manage customers in QuickBooks Online.

Please let me know how this goes and feel free to add updates about this. If you have further concerns about adding logo in QBO, simply leave a reply below. I'm always around and willing to help. Have a great week ahead and take care.