The code you posted does not make a whole lot of sense. It appears to be CSS code however there are no style tags. I looked at the source for your web page and the same snippet does not exist in the head section.
If you want to add a logo and style it, you should just place a image tag inside of a div tag in your header.php file or equivalent for your theme. It may look something like this,
<a href=”yourexternallink”><img src=”yourimagepath” alt=”” /></a>
Your corresponding CSS might look like this
Margin: some value;
Padding: some value;
I cannot put values for your margin and padding or know if these are even relevant for you to use without knowing what your header.php file looks like or how other elements on the page are positioned but this should point you in the right direction.