well you can't really.
you need to make the "play area" in one frame and then say something like
always centre frame on "object"
i think that the virtual size and frame size need to be bigger for the scrolling to work.
there are some good tutorials on the clickteam website
there is a way to do what nifflas games are like (scroll on edge of screen)
but i don't know how to do that
hope it helps