This video shows you how to use the free Open Live Writer for Windows to insert and edit content on your WordPress website.
Note that you can also accomplish the same thing on the Mac using MarsEdit. Although not free like OLW, the price is reasonable and Daniel, the developer, is very responsive to support questions.
Here is the CSS used to style the background as noted in the video:
#hs1txt { background-color: #ffffff; margin-bottom: 15px; padding-top: 30px; padding-left: 20px; padding-right: 20px; }