[Theme: Twenty Thirteen] Make the theme boxed

How do I make the theme boxed? I’ve tried adding containers. It works when the page/post content is longer than the size of the sidebar, but since I have a long sidebar, then some short content on some pages/posts, it looks very weird.

Weird since let’s say I made, for example:
#page {
background: yellow;
}

Index with longer content shows it’s fine, but once the content are short, some portion of the sidebar part have background yellow, any help?

Thanks!