Just go to a gym and start working with a trainer, either one-on-one or in small classes. It is important to find a trainer who recognizes where your father is,

Just go to a gym and start working with a trainer, either one-on-one or in small classes. It is important to find a trainer who recognizes where your father is, and scale exercises accordingly. You have to talk to the trainer himself, not just the guy on duty that day. Probably best at a small. Independent gym, not a chain. This might be expensive, but it is so worth it.