// For Vanilla WordPress
add_action( 'after_setup_theme', 'your_child_theme_setup' );

your_child_theme_setup() {
    add_theme_support( 'post-thumbnails' );
    add_theme_support( 'custom-background');
    register_nav_menu( 'primary', __( 'Navigation Menu', 'myTheme' ) );
    define( 'HEADER_IMAGE_HEIGHT', apply_filters( 'myTheme_header_image_height', 198 ) );
}

// For Genesis
add_action( 'genesis_setup', 'your_child_theme_setup', 11 );
function your_child_theme_setup() {
    ... your genesis code
}