CD,
Welcome along to this wonderful world of bikes. Lots of factors come into play but the most important thing is to just do it. Put the bike on the trainer or pull out that stationary and spin the pedals as long as you can stand. I usually go an hour on my Traveler (another of my shameless plugs for vintage Schwinns) while watching action films. I love car chases, any chase for that matter! The important part is spinning those legs while working up a sweat. Keep it simple at first. If you get into the whole fitness scene you can add the more analytical parts later.

Since you live in the northeast, you should think about building yourself a bike with studded tires. Since we've been in a snow drought here in NH, I've not ridden my "Snow Cycle" much. Hopefully tomorrow I'll log a few miles outdoors in the white stuff.