To display bank account information in your documents, you can add it directly on your Template.
From the main menu, select "Settings -> Templates" and "Edit" the templates you are use. The "Terms and Conditions" field on the bottom of the page can be used to type-in your bank account information. Don't forget to click "Save" when you are done.
This information will now be visible to your customers on every invoice you have issued using the template.