When you have uploaded your presentation eg to http://scivee.com/node/9271 the community tab will allow you to add it to this community provided you are logged in - otherwise you just see what communities it belongs to.
That tab allows no such thing. I currently have a movie uploaded and I am logged in, but I cannot publish it to our community...
For those who have uploaded, but not had your video added to teh community.. Seems only I can add it to the community - sorry for the confusion. When you are ready to have it added to the community send me an email with the URL and I will add it