Targetting the main timeline?

I’ve either cocked something up or I’m really confused about what I’m meant to be doing.

In AS2, I used to be able to get the main timeline to play through a variety of ways – _level0.play and _root.play being two such methods. But AS3 seems to be different.

_root isn’t there any more, I’m getting errors when I use _level0, and stage seems to refer to a set of properties and methods that have little to do with actually moving about the main timeline.

So how do I do it?
At a certain frame in myClip, I want it to tell the main timeline to continue playing. But I get various errors when I try different things. Like *‘call to a possibly undefined method play() through a reference with static type flash.display:DisplayObject’ *for example.