So you should put your tpl somewhere in skin1 folder, write your own php file and place into admin directory.
PHP is something like this:
Code:
<?php
require "./auth.php";
func_display("path_to_your_tpl/your_tpl_name.tpl",$smarty);
?>
where path_to_your_tpl is relative to skin1 folder
f.e. if your tpl is in skin1/admin it should be func_display("admin/your_tpl_name.tpl",$smarty);