Add custom woocommerce checkout fields

 <?php 

 // Hook in
add_filter( 'woocommerce_checkout_fields' , 'custom_override_checkout_fields' );

// Our hooked in function - $fields is passed via the filter!
function custom_override_checkout_fields( $fields ) {
     $fields['billing']['shipping_phone'] = array(
        'label'       => __( 'Phone1', 'woocommerce' ),
        'placeholder' => _x( 'Phone1', 'placeholder', 'woocommerce' ),
        'required'    => false,
        'class'       => array( 'form-row-wide' ),
        'clear'       => true
     );

     return $fields;
}

/**
 * Display field value on the order edit page
 */
add_action( 'woocommerce_admin_order_data_after_shipping_address', 'my_custom_checkout_field_display_admin_order_meta', 10, 1 );

function my_custom_checkout_field_display_admin_order_meta($order){
    echo '<p><strong>'. esc_html__( 'Phone From Checkout Form' ) . ':</strong> ' . esc_html( $order->get_meta( '_shipping_phone', true ) ) . '</p>';
}

?>