Hi there, cathy6.

Thanks for posting here in QuickBooks Community. I'm here to help and walk you through on how to customize your Invoice template in QuickBooks Online (QBO). 

Are you trying to add notes on the invoice template? If so, you can customize your invoice by adding a footer text. 

Here's how: 

1. Click the Gear Icon.
2. Select Custom From Styles.
3. From the New Style drop-down, choose Invoice. 
4. Select Content.
5. On the right side option, select the third pencil icon. 
6. In the Add footer text box, type-in the information you want to add on the invoice.
7. Click Done to apply the changes. 

However, if you're trying to adjust the font size and spacing, you can follow the detailed steps in this article: How to customize invoices, estimates, and sales receipts.

If you're referring to something else, please don't hesitate to leave a comment below. I'm always here to help you out.