How do I increase working area?

programming flash
1

I’m not sure where to look for help from this, since I don’t know what this is called.

I’m making a game with scrolling backgrounds. How do I make this canvas or work area bigger so I can see all of my platforms?

http://i26.tinypic.com/so93d5.png See what I mean?[URL=“http://i26.tinypic.com/so93d5.png”]