At the moment, new contacts must be added from the "Addressbook" which leads to "Contacts" or "Browser" or "File Manager" (don't know how the latter two could be used for this). It would be nice if one could as well directly key-in (or cut&paste) a number.
In addition: It seems, that a number (from "Contacts") which actually is not (yet) subscriped to the service, is just silently ignored as new contact without any message like "unknow contact".