Hi,
Right click the drive on the Desktop and select "Get Info." Next, you need Icons, and you can virtually use anything, even a random image. There are lots of free custom icons online, or you can make your own.
Once you have Icons that you want to use, pull up the Get Info screen of the icon itself, and select its preview in the top left corner area of the window to outline it in blue. Ctrl+C to copy it, and then go back to the Get Info screen of the drive and select its picture, and Ctrl+V to paste.
Hope this helps.