[K12OSN] Where is it?

[jconlon1 at elp.rr.com]

The following statement is in the help files for Totem player:

Proprietary Plugins

    You can add proprietary plugins to handle additional movie or audio
files. To add proprietary plugins to Totem Movie Player, click on the
Add Proprietary Plugins button.

My question is where is this button hidden?  I have searched everyting
in Totem player that clicks, opens, or does anything and I can't find
it.  HELP!  I need to be able to play the .asf video files from
www.unitedstreaming.com

Thanks
Pat