Change CSS for Blog Feed

I am using the Twenty-Thirteen theme with a child theme installed for customization. I want to tighten up the look of the blog feed page so that more posts can get onto a page. Twenty-Thirteen comes with too much white space for my liking.

Here is a link to my site to a page that shows a graphic of what the feed looks like on the right and how I would like to have it look on the left. Probably not at tight as shown on the left but I can adjust once I know what CSS elements to change.

Could someone point me in the right direction please?

Here is the link

Thanks,
Greg