im not sure what wwwroot and dirroot are really supposed to be but im guessing wwwroot is the absolute path to your web folder and dirroot is the uri to where these scripts are you are uploaded.
this should give you both
<?php
echo "Your wwwroot is {$_SERVER['DOCUMENT_ROOT']}.<br />\nYour dirroot is ". dirname($_SERVER['PHP_SELF']). "<br />\n";
?>
if you make that called info.php and save it in the same folder of this program you are trying to install, that should give you the info. if there is a documentation file or comments with the script, maybe you can tell us exactly what the programmer means by wwwroot and dirroot if my assumption here was wrong.