Do I have to place anything on my specific posts for it to work on all my blog?
(2) These widgets are for your readers' use. If they are already registered members of social bookmarking organizations then the widget provides a quick way to add a bookmark to your site.
If you would like to become a member of any social networking site then it's up to you to decide and to register.
(3) I know of no reason why you cannot go to =>Presentation => Sidebar widgets and rearrange your left sidebar widgets as desired or add to them. :)