Easy (hopefully) question about formatting.

Hello there helpful users of reddit. I have started my own blog less than a week age, and I have having an issue having my blog posts fit the screen the way I would like. I am having problems in locating a place or a feature where I can just make my whole page wider. Google has failed me and I cannot seem to find any CSS that would allow me to easily do this and there certainly isnt an area in the toolbox/editor that I can find to do this.

Let me be more specific. http://box5768.temp.domains/~whitegre/white-black-grey-part-1/ here is an example article. When you view this article it appears in a long thin column towards the left side of the screen, almost as if there is an invisible side bar that I cant get rid of. It is only using about 1/3rd of the browser screen space. I would like this article to be both centered and take up more screenspace/more space on the page so that the pictures can be bigger and so that the article just is not as LONG as it seems now. The whole website seems to be set up like this, justified to the left and more thin than wide, leaving too much empty space for my tastes.

Any help to center and spread this out for this page and all pages would be greatly appreciated. Thanks!