If you don't know how nor what you are doing, seek professional help. do not try to clean it yourself, because you will VERY likely ruin any value the coin may have had. Search the older posts on coin cleaning to get a feel for the members' sentiments regarding cleaning, cleaned coins, techniques and precautions.
There is not much you can do to help that coin. It is completely corroded. About all you could do would be to attempt to stop additonal corrosion. You should be able to do that by using a commercial coin dip. But I warn you, coin dips are an acid. Too long in the chemical and even more metal will be eaten away than already has been. Not long enough and corroded material will be left on the coin to continue its destruction. Your best bet is to sell or trade the coin and get another that is problem free. You could do that for just a few dollars.
