1. Show the package contents of the app.
2. Open resources and look for the icon, it should have the extension ".icns".
3 ( if needed ). If it's not already, make your new icon a icns file.
3a. Open the image in Preview.
3b. Press "Shift + ⌘ + S".
3c. From the drop-down menu, choose icns and export it to the desktop.
4. Name the new icon the same title as the one already there.
5. Replace the old icon with the new icon.
6. Open the new icon in Preview.
7. Press "⌘ + A" and then copy it.
8. Go to the app you wish to change.
9. Highlight the app and press "⌘ + I"
10. Click the icon on the get info window and paste.
11 ( if needed ). If the app prevents pasting, do the following:
11a. Click the the lock at the bottom right of the get info window and enter your password at the prompt.
11b. Click the + at the bottom left and add your current administer account
11c. Change your administer permissions on the get info window, if isn't already to read and write.
11d. Click the icon on the get info window and paste.
