changing header image size

I have bought the daily dish child these from studio press and have it installed. I want to upload a logo as my header. the allowed space is ridiculously small. I was given these instructions below by studio press to correct it – and I have done this –
but it still looks tiny when it shows up on the page

Help!

In your functions.php file of your Daily Dish theme, this is what sets the width and height uploaded. Edit to what size would be best fit for you
//* Add support for custom header
add_theme_support( ‘custom-header’, array(
‘header-selector’ => ‘.site-title a’,
‘header-text’ => false,
‘height’ => 80,
‘width’ => 400,
) );

In style.css edit this to be same size you added to function above
.header-image .site-title > a {
background-position: center !important;
background-size: contain !important;
display: block;
height: 80px;
margin: 0 auto;
max-width: 400px;
}