Reducing Whitespace-Wordpess 2012 Theme

I am using WordPress 2012 as the theme for my website (saint-albans.org). There is a lot of white space–which I’d like to either totally eliminate or, at least greatly reduce–at the bottom of the website’s homepage. Would it be possible to do this through CSS modification or should I just add more items to the homepage? If a CSS modification is necessary, where exactly should I make the edit(s)? I have the Childify Me plugin to create a child theme. Thanks for any advice!