Hi
There should be the editor tab under “Appearance”, do you not have it?
Or you can edit the files in any other text editor.
You can change the logo allowed size by changing the “functions.php” on line 60 to be:
add_theme_support('custom-header', array(
'default-image' => '',
'width' => 290,
'height' => 110,
'flex-width' => true,
'flex-height' => true,
'header-text' => false,
));
Then you might also need to look in the css file and search for the class “.site-branding” and change it accordingly, and depending on if you’re using “.site-header-one” or “.site-header-two”. as they have “height” set to them.
Hope that helps.