Place module in /modules/ and include the call in your bootstrap.
class Model_Category extends ORM_MPTT {
}
$cat = ORM::factory('Category_Mptt');
$cat->name = 'Music';
$cat->insert_as_new_root();
echo 'Category ID'.$mptt->id.' set at level '.$cat->lvl.' (scope: '.$cat->scope.')';
$c1 = $cat; // Saving id for next example
$cat->clear(); // Clearing ORM object
$cat->name = 'Terminology';
$cat->insert_as_last_child($c1);