All of us have our own way of learning new things. A friend told me to watch streams of tanks on raids to understand what they do from their point of view, though most of the time I raid on my dps and at the same time watch what the tanks do, look out for tank busters, notice when they swap, etc. And when I have cleared the fight on dps, I'll go for a couple of practice runs on tank then a "duty completion" run to make sure I cement my confidence in clearing the content as a tank. But really whichever suits you best having someone to call out is also immensely useful!