Image size

I set (to test) the image size on 48px. The first image size is good but the mouse-over image is still big. Also the other sizes gives the same problem.

48 px is still too little so i want to set a new size. I found this code but i don’t know where to put it in the function.php.

add_filter( ‘menu_image_default_sizes’, function($sizes){

// remove the default 36×36 size
unset($sizes[‘menu-36×36’]);

// add a new size
$sizes[‘menu-50×50’] = array(50,50);

// return $sizes (required)
return $sizes;

});

The page I need help with: [log in to see the link]