Installing FreeType Library on Plesk 8.2, how?

[M vd Lingen]

I want to install FreeType Library on Plesk 8.2, but how do I achieve this?

Can somone explain how I should / can install it?
I already tried searching the forums, but alas no succes.

Thanks for your help and time.

//edit

Cause when I use the following:

<?php
// Set the content-type
header('Content-type: image/png');

// Create the image
$im = imagecreatetruecolor(400, 30);

// Create some colors
$white = imagecolorallocate($im, 255, 255, 255);
$grey = imagecolorallocate($im, 128, 128, 128);
$black = imagecolorallocate($im, 0, 0, 0);
imagefilledrectangle($im, 0, 0, 399, 29, $white);

// The text to draw
$text = date("F j, Y, g:i a");
// Replace path by your own font path
$font = 'arial.ttf';

// Add some shadow to the text
imagettftext($im, 20, 0, 11, 21, $grey, $font, $text);

// Add the text
imagettftext($im, 20, 0, 10, 20, $black, $font, $text);

// Using imagepng() results in clearer text compared with imagejpeg()
imagepng($im);
imagedestroy($im);
?>

It displays an empty image. So I am thinking I am having a problem with the FreeType Library (or lacking one).