/**
 * Append the popup content to the popups array
 *
 * @param  array $fields Popup fields array.
 *
 * @return array         FIltered popup fields.
 */
function append_popup_content_field( $fields ) {

    // Append the popup content to the popup container
    $fields['popup_content'] = array(
        // 'wrap' => 'div',
    );

    // Re-order the popup fields into the order you'd like
    $new_order = array(
        'title',
        'announcement_image',
        'announcement_date',
        'popup_content',
        'content',
        'next_prev_links',
    );

    $new_fields = array();

    foreach ( $new_order as $field_name ) {

        $new_fields[ $field_name ] = $fields[ $field_name ];

    }

    return $new_fields;

}
add_filter( 'timeline_express_popups_fields', 'append_popup_content_field' );