I'll show you the steps to edit the template's footer, mike68.
When you're on the Content section of the invoice template screen, you will not find any links to edit each section. If you'll notice, there are small pencil icons in the upper right-hand corners of each section (header, body, footer). That's what you need to click to be able to add the bank details.
You can also click on each section directly to open them up. Now on the left side of the page, you'll be given options on what details to add. For the footer's display, you can add Discount, Deposit, or Estimate summary as additional fields.
Once you're done editing the template, just click Done and you're good to go.
I've added a screenshot for you too.
Don't hesitate to leave a reply if you have additional questions about this. Thanks for dropping by.