How to set post format

Hello

I’m using your wonderful plugin to allow my users to enter posts with featured images to our photo blog site.
The small problem I have is that I’d like to be able to set the post format to ‘image’ instead of ‘standard’. I’ve been looking all over to find out how to do this and found these instructions:
http://codex.wordpress.org/Function_Reference/set_post_format

<?php set_post_format($post->ID, ‘image’ ); ?>

But I’m not a coder and I don’t know where to put the code. Are you able to tell me where to put this code, or tell me if there’s a better way for me to make the change? It would be ideal if I could make a change in a place where I won’t lose it during an upgrade, but if that’s not possible, that’s ok.

Thank you very much

Vicki

http://wordpress.org/plugins/wp-user-frontend/