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 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.