It should be in the style.css that you do it, but if it’s not, you can use the tinyMCE plugin for it. http://www.wpbeginner.com/beginners-guide/how-to-change-the-font-size-in-wordpress/ shows you how to use it. Let us know if that helps.
You can actually put anything you want in every applicable field and use it to be added on your detailed brand descriptions, in footer or even in header. You can manage all of those changes the way you wanted, just refer to this http://eatmywords.com/portfolio/names-in-a-nutshell/ for future reference.