Drag to the Resources folder in Xcode. You will be asked for some specifics of your png file. It's suggested to select Copy items into destination group's folder. And click Add.
The png file will be placed here:
Click your <xxx>-info.plist (it's HelloXcode-info.plist in my project) to edit the properties.
Double click on the empty field with "Icon file" properity, and type in the file name of the icon.
Save it and Click Build and Go again,
Exit your Application in iPhone Simulator, it can be noted that the icon of your application is updated.
