sforsman1 on "Link logo to homepage (Twenty Twelve)"

Hi, I have a quick question. I'm using Twenty Twelve and I figured out how to add a logo (below is what I added to style.css in my child theme) but I'm unsure how to make it a link to the homepage, so please let me know how I might be able to do this. My site is http://www.shannonforsmanphotography.com. Thanks!

#masthead hgroup { position: relative; }
#masthead hgroup:before {
content: url("http://www.shannonforsmanphotography.com/wp-content/uploads/2013/06/logo1.png");
display: block;
width: 360px;
height:92px;
position: absolute;
}