I installed Xcode 4, it has very cool features. I developed my new app with Xcode 4 and its time give it to client for their testing.
The problem is the that I am
You could also select Product -> Build For -> Archiving, then expand the Products folder in the navigator, right-click the app and choose Show in Finder.
~/Library/Developer/Xcode/DerivedData/{app name}/Build/Products/Deployment/
You need to use the Product->Archive function instead. You can then access the archive from Organiser. Share the archive and then save it to disk - this creates a .ipa file which can then be distributed for testing.
As ever though, comprehensive documentation on this matter from Apple will guide the way.