Just visit any GP, if your problem is beyond the cure of normal medicine like viagra etc., then you can look for specialists. GP around your working or living should be good enough to rectify your problem if you have impotent or impotent due to other diseases. If yours is too short and need operation to make it longer, or you want to implant steel balls in your kok then you need a careful selection of the doctor and consideration of the consequences if operation not successful.