There are several different methods for attempting to deal with alcoholism. One common practice is to have what they call an intervention. This is where, unbeknownst to the alcoholic, all family members and maybe very close friends approach the alcoholic as a group to give an ultimatum of going into a medical facility for detoxification and treatment for alcoholism immediately, that day/night, or losing their family. Part of alcoholism is denial, so the idea here is to get enough loved ones to outnumber the alcoholic's claim of not having a problem.
As already mentioned, you may want to contact a local alcoholic recovery group (AA or any other) for more detailed advice.