Header logo dimension

Hi! Sorry, there’s a way to modify the dimension of the header logo? I tried in different ways but i couldn’t. I’m not expert with php. The problem is that i’d like that the logo would be of the dimensions i say, at least bigger than the ads in the ad widget of the header.
Thank you in advance
http://allabouttravel.altervista.org/

Hi,
you don’t need to edit php files. you only need to add this css code using custom css plugin:

img.site-logo {
  height: 170px;
}

Hi Awan, tank you so much!

I did it but nothing changed :-\