Paste

//In Functions.php I added the artist from the example

/**
 * Add a field to the add post area
 *
 * @uses `wpuf_add_post_form_description` action hook
 *
 * @param string $post_type the post type of the post add screen
 * @param object|null $post the post object
 */
function wpufe_artist( $post_type, $post = null) {

    $artist = ( $post != null ) ? get_post_meta( $post->ID, 'artists', true ) : '';
    ?>
    <li>
        <label for="song_artist">
            Artist <span class="required">*</span>
        </label>
        <input class="requiredField" value="<?php echo esc_attr( $artist ); ?>" type="text" name="song_artist" id="song_artist" minlength="2" />
        <div class="clear"></div>
    </li>

    <?php
}

add_action( 'wpuf_add_post_form_description', 'wpufe_artist', 10, 2 );


// In Add post, I changed to output the errors
        //if not any errors, proceed
        if ( $errors ) {
            echo wpuf_error_msg( $errors );
            return;
        }