Start with reading everything you can get your hands on about addiction/alcoholism. Get armed with information not for him, but you. Be gentle with yourself as you discover Ah Ha moments. I still have them daily and have been doing this for many years. Sometimes I can read something 100x and it not sink in. Maybe because I am not open, or just plain stubborn. The one I grapple with is that his addiction is not about me. The 3 C's. It may hurt but I cannot take it personally.
Lots of great advice can be found in these forums. I found for myself the best thing was to start in F&F, then Alcoholism and New Posts. It has been so beneficial to see addiction from both sides. I have been to Alanon and open AA meetings, too.
Hang in there!