I need to add locations on the invoice in such a way that it shows on the printed invoices.

Welcome to QuckBooks, accounting374.

Currently, showing the location on the printed invoice isn't possible. You can add them as a custom field to make it visible on the printed invoice. Let me guide you with the steps.

1. Click the Gear icon, then select Accounts and Settings.
2. Choose Sales.
3. In the Sales form content section, click the pencil icon.
4. Under Custom fields, click the Custom Fields hyperlink.
5. Click the Add field, select Transaction info.
6. Type the Location name on the Name field.
7. Under the Type field, select the Drop-down list option.
8. Enter different items for location.
   
9. Make sure to enable the Show to customer option to show location on the invoice.
10. Click Save.

For more information, please check this article for more information: Customize Sales Form By Location.

For future reference, you'll want to run reports in QuickBooks Online (QBO): Run Reports In QBO.

If there's anything you want to help us with, let me know so that we can help.