Top margin for footer

This is a really stupid question – I am actually kind of embarrassed to be asking but…all I am trying to do is add a 30px margin to the top of my footer. When I inspect the element with firebug and add the margin in the layout tab – it corrects my problem – then when I click css it shows this:

element.style {
margin-top: 30px;
}

– I don’t really know where to put this css – element.style doesn’t seem to specify the footer at all – If I just put that in my css I find it highly unlikely that it will change my footer. Do I have to somehow incorporate it into my footer.php or what? my URL is http://www.daily-mash.com – if you look at the footer you can see what I am trying to correct. Any help is greatly appreciated – thanks!