I am trying to build an app, following the live cod accedemy. But at the beginning I have already few problems

1) The Test button is not "clickable"
2) when I try to save standalone application I see this message: performing iOS device builds requires the iOS 5.0 SDK platform to be installed (available with Xcore 4.2)
I have a mac 10.6.8 and from the apple developer page I have download the Xcode 3.2.3 (because 4.2 is for mac Lion).
Hellllppppp me please!!!!!
thank you thank thank you