How to add php code into vb4 template?

[postcd]

How to add php code into vbulletin 4 template?
i want it only on the index page (forums listing)

the php code to add:

<?php
// THE FOLLOWING BLOCK IS USED TO RETRIEVE AND DISPLAY LINK INFORMATION.
// PLACE THIS ENTIRE BLOCK IN THE AREA YOU WANT THE DATA TO BE DISPLAYED.

// MODIFY THE VARIABLES BELOW:
// The following variable defines whether links are opened in a new window
// (1 = Yes, 0 = No)
$OpenInNewWindow = "1";

// # DO NOT MODIFY ANYTHING ELSE BELOW THIS LINE!
// ----------------------------------------------
$BLKey = "***";

if(isset($_SERVER['SCRIPT_URI']) && strlen($_SERVER['SCRIPT_URI'])){
    $_SERVER['REQUEST_URI'] = $_SERVER['SCRIPT_URI'].((strlen($_SERVER['QUERY_STRING']))?'?'.$_SERVER['QUERY_STRING']:'');
}

if(!isset($_SERVER['REQUEST_URI']) || !strlen($_SERVER['REQUEST_URI'])){
    $_SERVER['REQUEST_URI'] = $_SERVER['SCRIPT_NAME'].((isset($_SERVER['QUERY_STRING']) && strlen($_SERVER['QUERY_STRING']))?'?'.$_SERVER['QUERY_STRING']:'');
}

$QueryString  = "LinkUrl=".urlencode(((isset($_SERVER['HTTPS']) && $_SERVER['HTTPS']=='on')?'https://':'http://').$_SERVER['HTTP_HOST'].$_SERVER['REQUEST_URI']);
$QueryString .= "&Key=" .urlencode($BLKey);
$QueryString .= "&OpenInNewWindow=" .urlencode($OpenInNewWindow);


if(intval(get_cfg_var('allow_url_fopen')) && function_exists('readfile')) {
    @readfile("http://www.backlinks.com/engine.php?".$QueryString); 
}
elseif(intval(get_cfg_var('allow_url_fopen')) && function_exists('file')) {
    if($content = @file("http://www.backlinks.com/engine.php?".$QueryString)) 
        print @join('', $content);
}
elseif(function_exists('curl_init')) {
    $ch = curl_init ("http://www.backlinks.com/engine.php?".$QueryString);
    curl_setopt ($ch, CURLOPT_HEADER, 0);
    curl_exec ($ch);

    if(curl_error($ch))
        print "Error processing request";

    curl_close ($ch);
}
else {
    print "It appears that your web host has disabled all functions for handling remote pages and as a result the BackLinks software will not function on your web page. Please contact your web host for more information.";
}
?>

Update: one can do this:
vBulletin Admin area / Plugins & Products / Add New Plugin
As a Hook location you can use navbits_complete and it should load the php code on all pages of the forum including index. To show it only on thread pages, use "fetch_foruminfo"
Plugin is Active = yes
As a PHP code, do NOT enter <?php ?>, you should add code right away