Question about modifications

Hi,

I purchased your BlackFyre WordPress theme last night and I was wondering if there is a way to edit the size of the header (where the logo is), and the height of the navigation bar?

I’m new to WordPress but have some knowledge of HTML/CSS so I’m kind of lost looking through all this WordPress stuff. Am I wasting my time looking for a way to edit the CSS? Is it possible to edit those things, or is it already set as is for the WordPress theme?

Thanks