Hi there, you first have to widen the content area with CSS, and then enter the new content width in the Content Width box, which is the value WordPress uses to size your images and videos that are inserted full width. As it stands, the overall content area is about 700px in width but there is padding of 27px on each side, which means the actual content width is 700 - 54 = 646.
Add the following and adjust the width as you desire. The width had been in em units, but I switched it to px to make it easier. The content and sidebar are in % widths, so there isn't an exact correlation between the overall width increase and what you can enter into the Content Width box. You will have to play with that a little to see what works best. If you increase the overall width by 200px, you should be able to use 790 for content width.
Oh yeah and by the way, YES to more coding ladies. :)