Missing post-format from Twenty ten?

I’m A WordPress newbie who has Twenty ten running.

I want to use the gallery post format.

But when I edit a post I do not see the post formats options on my admin screen.

1. http://en.support.wordpress.com/posts/post-formats/ says that the options box is under the publish button – but it’s not there

2. So I tried adding a child theme with the function add_theme_support( ‘post-formats’, array( ‘aside’, ‘chat’, ‘gallery’, ‘image’, ‘link’, ‘quote’, ‘status’, ‘video’, ‘audio’ ) );

2a. I took this from http://lisasabin-wilson.com/wordpress-3-1-post-formats-reference

3. This didn’t work – I also found this comment about development beta version of the theme “Something strange we discovered is that if you add this line to the child theme of Twenty Ten it does not have the desired effect.”

So I’m a bit stuck. Any ideas?