After having defined your name and address (and maybe also your VAT number) in the Details field under Settings > Accounting, you may wonder where you can insert your billing information (bank account number, etc.) so that they appear in every document you create. Well, in the footer of the document!
For that, you have to go in Settings > Document and email configuration. You select the configuration in which you want to add a footer and you click on the Terms and footer tab.
Then, at the bottom of the page, you have a Footer field where you can enter all the information you want (and format it as you wish). You can also add a variable to make sure the document number is displayed on each page (which is mandatory in certain countries).
Then, click on Save.