;
, You can press "Cmd + I" on the keyboard, or press down the option key while you click the folder and then select "Get Info."

, Do this using Preview.
 Press "Cmd + A" to select the image and "Cmd+C" to copy it.
 Click on the folder image at the top left corner of the window and then press "Cmd + V" on the keyboard to paste the image.
Click any folder of your choice.
Bring up the info page.
Open any the image you want to use as an icon.
Select the image and copy it.
Replace the folder icon.
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