How to launch UIViewController that is embedded in UINavigationController

Question

I have TabController with 2 tabs A &B
Tab A: UINavigationController1-->Controller X--->Controller Y
TAB B: UINaviagtionController2-->Controller A --->Controller B --->Controller C

In the Tab Controller, I have a button that I would like to launch Controller X. How do I get X with its navigationBbarController? I can get to X, but doesn't show the navigation?

Thanks