Pretend that you are going to edit your story, click on "Edit" back in the main story section where your story is posted.
Once in the editing window, right click and choose "select all" and then right click and choose "copy".
Abort the editing session, and go to your archive here. Click on "New Post". This should give you an editing window.
Right click and choose "paste". The entire text of your story should appear in the editing window. Put the title in the little title window, and click on "submit".