There is a full width page template that you can use to make your pages full width. When you’re editing a page, look in the right hand column and you should see the drop-down menu for templates. From there you can choose the full-width one and update your page.
If you absolutely want to make everything: pages, posts, blog archives and so on, full width, then you can do that globally with a bit of CSS. Here’s how:
Go to the Theme Options page and select the Styling tab.