Old galleries and new galleries

Ok… maybe I didn’t understand how the new galleries work in WP 3.5, or (better) how I can manage the old ones with the the new image uploader. I mean, how can I recover the old galleries, the simple galleries associated with the posts until WP 3.4? How can I edit them or simply delete them? Some plugins or themes still display them on the front-end, but I can’t find them anywhere on the back-end.

Thank you 🙂