When logged in on your pos.icio.us page, you should be able to go in "edit" mode and start arranging your tags (using click-and-drag). "view" mode will let you browse your tags and urls. When you post a url using del.icio.us, you should see your cloud of positioned tags. Your cloud is composed of two different zones: a grey area with a list of unpositionned tags, a white one where you can position your tags.