Open “functions.php” of your theme and write below code.
if (!function_exists('hs_setup')) :
function hs_setup()
{
add_theme_support(
'custom-logo',
array(
'height' => 300,
'width' => 250,
'flex-width' => true,
'flex-height' => true,
'unlink-homepage-logo' => true,
)
);
}
add_action('after_setup_theme', 'hs_setup');
endif;