[Plugin: NextGEN Gallery] insert random picture in a page

Hi !

I would like to insert a random picture of my gallery in my website but I did not manage to do it.

First of all I tried to insert [random max=1] as it is said here : http://wordpress.org/extend/plugins/nextgen-gallery/faq/ but it displays one thumnail by random. And I would like the entire photo

Then I found we can insert this code :

<?php
if (function_exists("nggDisplayRandomImages"))
nggDisplayRandomImages(1,600,600);
?>

I inserted the code in the page, but the code displays on the website, I guess I did not insert this code in the right place.

Could you please tell me where to insert this bloody code?

Thanks in advance…

Aj