It's the same as any other app that ensures there is only a single instance of its process (per desktop): If you want to run the whole thing as admin you have to exit it completely and run that as admin.
Going back to the original question, no there's no way to run multiple instances (on a single desktop; i.e. ignoring Terminal Services etc.). A single instance handles all windows and if another instance is run it just tells the original instance to open another window.