Start small. Zwift can be a fun way to pass the time on the trainer, but I'm not sure I would jump right into a structured training. Maybe spend a couple of nights a week for the first couple weeks just riding around and checking out the virtual scenery. You'll want to make sure that your bike fits you and you have your set-up all figured out: good display, good fan, and especially good fit. After you have gotten comfortable, maybe think about a bit more structure (and make sure that the structure calls for adequate recovery on both a micro and macro level.)

On edit: in addition to the Indoor Training subforum, you might want to check out the 50+ subforum too.