There are many ways on how to launch a popup from a popup, and I'm going to demonstrate here a "backingBean-based" of launching this.
So why go programmatic? The reason for this is because most of the time, I would prefer launching one popup at a time, meaning that when I call the second popup, I first make sure to close the current popup.
So a straight forward sample in launching the popup declaratively looks like this.
As you might already know, this is achieved by simply calling af:showPopupBehavior.