The quickest way would be to import your coin into the Library then take that symbol and put it on the work area and use the Tweening function to automatically create all the frames to make the coin spin.

Here are some tutorials that should help:
http://www.echoecho.com/flashtweenings.htm
http://www.webdevelopersnotes.com/tutorials/adflash/shape_tweening_in_flash.php3

Also, if you want the background of the image to be transparent you will need to bring the image into Flash as a .png to preserve the transparency settings of the image.