There are plenty of training schedules that you can look at on
Bicycling Magazine's free web site. Keep in mind that most, if not all, are for much younger riders and are geared more toward racing than endurance/fitness and fun. Almost all of them include a combination of intervals and spinning which has worked quite well for me, but I think the best way is to just get out and ride as often as you can. For you guys up in the cold country, winter doesn't sound like a good time to start riding, even on a trainer. Trainers can get boring after a while and sticking with it while doing the exact same thing each time can burn you out. But if you have no choice but to use the trainer, try different things each time so you break up the monotony; intervals one day, spinning the next and throw in some "just get on the bike and pedal" rides. You can try some of the training videos/software that's available if you want to go all out. The Sufferfest series of training videos is a good place to start.