Personally I like to place my business address at the bottom of the page or the footer. To do this go to the floating bar and click on the button, 'Switch Between Header and Footer.' This will open a dotted box at the bottom of the document. You can type your office address here or anything you see fit for your letterhead. Again you can format the text by choosing the font, font size, color, align the text, etc.
Whether you are a technical writer working for a single firm or a freelance writer working for many companies, you can benefit from creating templates for your documents. In the long run a good outline will save you time and effort, and deliver that elusive consistency to your material that users will appreciate. Here's how you go about it.