To know how to customize the documents you create using LSP.expert (logo, document templates, terms, etc.), see this article: https://help.lsp.expert/en/articles/1863932-can-i-customize-the-documents-i-create-with-lsp-expert
You can insert your billing information (bank account number, etc.) in the footer of your documents.
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.
For each document, you can add a footer:
You can enter all the information you want (and format it as you wish). Then, click on Save.