The same way you train a younger dog, but, with more patience, persistence, time and always be consistent. At 8 yrs old they have habits that need to be worked thru. It can be done. I had a guy who had a 12 yr old lab in one of my classes. Everything turned out great, he just needed to come to every class and listen to what I told him to do, and I had to listen to his problems and concerns and fix what I could. Get into a good class that teaches positive reinforcement training. Good Luck..