How to reference objects in xcode 4 storyboard

In the storyboard I dragged over a viewcontroller (B) so that the storyboard now contains two view开发者_JAVA百科controllers... B and the original (A). I put a button on A and dragged it to B to make a button click on A bring up B. On B I dragged a label and a button. I want to click the button on B to make the label on B show "hello world". How do I procede?

If you are member of iOS program, then look for video from Session 309 of WWDC 2011 called 'Instroducing Interface Builder Storyboarding'.