Need help with opening .mpg in IR

I've read all the tutorials, but i still can't get it to work. Whatever I do, when it opens the.mpg file, all I can see in the animation bar is the first frame. I can pretty much do nothing with it, cause it's only one pic. I really wanna know how I can select different layers and open them etc...cause I really wanna work with it etc...etc...Any help would highly be appreciated!