There are 2 ways to use as PHP function:

First:

$args = array(
    'id'                 => 'uniqueIDHERE',
    'title'             => "Title Here",
    'title_icon'        => '',
    'counter'             => 'until',
    'until'             => array( 12, 27, 2013, 16, 53 ), // month, date, year, hour, second
    'cLabels'             => array( 'Years', 'Months', 'Weeks', 'Days', 'Hours', 'Minutes', 'Seconds' ),
    'cLabels1'             => array( 'Year',  'Month', 'Week', 'Day', 'Hour', 'Minute', 'Second' ),
    'compactLabels'     => array( 'y', 'm', 'w', 'd' ),
    'format'             => 'dHMS',
    'expiryUrl'         => '',
    'expiryText'         => '',
    'alwaysExpire'         => false,
    'compact'             => false,
    'onExpiry'             => '',
    'onTick'             => '',
    'tickInterval'         => 1,
    'bg_color'             => '#f6f7f6',
    'counter_image'     => '',
    'counter_color'     => '#444444',
    'label_color'         => '#444444',
);

echo the_countdown_pro( $args );

Second: Use the shortcode generator to help you generate the shortcode attributes and do action to the shortcode function:

do_shortcode('[countdown id="1377772338" format="dHMS" serverSync="true" alwaysExpire="false" compact="false" tickInterval="1" font_size="24" bg_color="#f6f7f6" counter_color="#444444" label_color="#444444" counter="until" until="12,27,2013,16,53" labels="Years,Months,Weeks,Days,Hours,Minutes,Seconds" labels1="Year,Month,Week,Day,Hour,Minute,Second" compactLabels="y,m,w,d"]');

NOTE: Please drag one widget to your sidebar OR Inactive Widgets area to pull the countdown scripts and styles.