Customizing wordpress "login screen." Add this to wp-content/themes/YOUR_THEME_FOLDER/functions.php

WP custom login

// Custom login page. Modifying logo image, link and title.
function my_custom_login_logo() {
    echo '<style type="text/css"> h1 a { background-image:url('.get_stylesheet_directory_uri().'/img/MYLOGO.png) !important; }</style>';
}
add_action('login_head', 'my_custom_login_logo');

function namespace_login_headerurl( $url ) {
    $url = get_bloginfo( 'url' );
    return $url;
}
add_filter( 'login_headerurl', 'namespace_login_headerurl' );

function namespace_login_headertitle( $title ) {
    $title = get_bloginfo( 'name' );
    return $title;
}
add_filter( 'login_headertitle', 'namespace_login_headertitle' );