How do I edit the layout of an invoice?

This forum is for code related issues on your site.

If you are using Wix Invoices then you need to be going through Wix Support and their own support pages for it as well.
https://support.wix.com/en/article/contacting-wix-support
https://support.wix.com/en/ascend-by-wix/wix-invoices

However, you can’t currently change the design of Wix Invoices.
https://support.wix.com/en/article/request-customizing-the-invoice-design-in-wix-invoices

To do what you are asking for will mean that you would currently have to make up your own invoice form and populate it with all the data through code yourself.