How to set the Application Icon with X-Code:
1) Double-click on your projects target.
2) Select the Properties Tab
3) Enter the name of your icon file (minus the .icns extension) in the "Icon File" text field.
4) Drag your icon file from the Finder to the "Resources" folder (to add the icon file to the project)
Now "Clean" the project and build fresh. Your app should now have it's custom icon in the finder
While you are in your Targets properties section, be sure fill in the "Identifier" section in reverse domain fashion. ie... com.mycompany.appname
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