Find the icon you want to change. Go to the folder that contains the file you'd like to alter. You can change the icon of most folders, applications, and documents. Certain special icons cannot be changed this way, including the Finder and Trash icons. You can change them with the system folder method , or using downloadable software such as LiteIcon or Candybar for older OS X versions. Open the information window for that file. Select the file by clicking on its name or image.
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Control -click the file and select Get Info from the drop-down menu. A new window should open with information about that file. Select the image in the top left. The file icon is in the top left corner of this window. Click it to select it, and you should see it highlighted in blue. Paste your copied image. This should change the file icon to the image you copied earlier.
This will only change the icon for that specific file, not for all files of that type. If a window pops up asking for a password, you are trying to change a file you do not have full access to. These files can only have their icons changed if you enter an administrator password, or if you log on to an account with access. If you think your account should have access, expand the "Sharing and Permissions" section at the bottom of the Get Info window.
Know the risks. This method shows you how to access the folder where all system icons are stored. This lets you change the icons for special items such as Finder and Trash, or to change default icons for an entire file type. Overwriting important icons or making a mistake here can make your computer very confusing to use. Log in to an administrator account.
Only an administrator account can access this folder. Open the Go to Folder window.