Assuming you're up to date on CS6 updates, and you have Xcode installed, you do this:
In your FLA that is set to use AIR 3.4 or later, look in the application settings, General tab.
You should see a field labelled "iOS Simulator SDK:". In there you put the full path to the Simulator. The path will most likely be:
/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator6.0.sdk
Once you have done that you should be able to do both Control/Test Movie/on iOS Simulator, and Debug/Debug Movie/on iOS Simulator.
If you do the debug version, wait until the publishing progress has gone away, and the Simulator is open in the background, and then select Debug/Begin Remote Debug Session/ActionScript 3.0. Once Flash is "waiting for connection", go over to the Simulator and open your app.
You may find that the app icon is on the second page of icons. As you would on iPhone you can move the icon either to the dock of the simulator, or to the first page of icons. Then when you do further tests the app will be installed into that location.
Using the simulator will save you hours of time!
Oh, one other thing - you can simulate multitouch by holding down the Option key, which will give you two mirrored finger points on the simulator screen, which is good for testing pinch actions. If you also hold the Shift key you will be able to simulate pan actions.