How to add image to gallery

I have a little test site using Drupal 6.2, with one gallery with three images in it. The image nodes also belong to a book. The gallery was created with an earlier version of image, either image-6.x-1.x-dev-2008-Apr-01.tar.gz or image-6.x-1.x-dev-2008-Apr-11.tar.gz.

Now I can't add images to the gallery. I'm not sure if it's because I've forgotten how to do it, or if there is a bug in 6.x-1.0-alpha1.

Please enlighten me.

(By the way, is there any discussion forum for the image module, where this question perhaps would fit better?)