I'd say that in your first year on the bike, base training isn't going to do you a lot of good. Just ride your bike however you want to.

At the end of year 1 (next fall/winter), your body has come along adapting to cycling, so here is where base training might do you more good for the following season.

I wouldn't, personally, work on base miles on my trainer. I would do it earlier in year (fall to late fall), and this is where you want to do LONG rides. How long depends on how long you're used to. Build up to it...don't just jump into a 4 hr ride if you've never ridden longer than 2, for example. So you want to take it easy enough that you can complete the long ride but that isn't too easy, shooting for a pretty steady pace. I say don't do it on the trainer, just because my butt (and mental health) wouldn't be able to handle 3-4 hrs on my trainer. The endurance base helps make you more efficient. It helps you go longer, lower your heart rate, and improve your recovery time.

Then later in the winter turning to early spring, use your trainer workouts for 1) recovery or 2) intervals. Then try to sneak in some moderately long rides outside if you can, or head out and do hill repeats or other strength or speed drills. Having an endurance base at this point will help you in your interval training. You'll be able to recover faster. Your cruising tempo will be easier and at a lower heart rate than it used to be (in year 1, for example). So then you will benefit more from the interval training since your standard rides are no longer putting you into the red so much.