Welcome to TE! The best way to get comfortable riding in traffic is to, well, ride in traffic. Take a basic skills class, then get used to roads by riding early weekend mornings or during the day. (Though the weather is getting sadly less conducive to that!) Do what you feel comfortable with.

I've had my bike for going on three years. (Her second "birthday" was in July.) The first season, I barely rode at all. My second season, I rode a bit more, but it was lots of short rides (no more than 10 miles most of the time). This year, I've essentially tripled the miles that were on my bike. Alas, due to the fact that I have to actually continue my education, I'm not riding a lot right now. Once I'm done with classes and am on a lab schedule, you can bet I'm tweaking it so that I can ride before going in in the morning!