ZC 2.0.1 Bootstrap template and OPC.

Is there a way to control the layout of the checkout page in the Admin, or is it CSS or template-based?

I currently have the checkout information displayed in 3 columns underneath the text Checkout, with each column being 1/3 of the width of the container.
I want each component of the checkout section to take up the fill width of the container.
I've achieved this result in a browser using development tools, but am unsure of the correct way to go about it.