You can find different fonts it the Library (or in my bio, wink wink). Once you've found one you want, save the file (by clicking the applicable link) and, if it comes in a .zip file, extract the files so that you have a .ttf file. If you're on a Mac, you can double-click it and the Font Book application will take care of it. If you're on Windows, what you do depends on what version you use. If you have 7/8/Vista, you might be able to right click -> install, otherwise you'd have to put it in the fonts folder (click here or use Start Menu -> Control Panel -> Appearance and Themes -> Fonts).