Well, experiment. Breathing is something you do all day without interfering.
So interfere. Try shallow breathing, deep breathing and everything in between.and notice what feels good this moment stick with that for now. If it becomes forced allow yourself to change to something that feels better. Short in, long out. Long in and short out. Again what feels good right now. If it no longer feels good try changing.
There's no rules about breathing a certain way. What you want is a sense of ease. And that differs in different circumstances. Where does this kind of breathing increase a sense of wellbeing. And if it feels good in the belly and not in the chest, what kind of breathing feels good in your chest. How does the belly feel when you do that. Just get to know your breath. And go with what feels bets in that moment. Just notice what happens to your breath when it becomes uncomfortable. Investigate a little, then try to find a sense of breathing with ease somewhere in your body and rest there for a while. It takes time and practice. But it's nothing magical. You are allowed to beathe anyway you like. And then magic can start to happen.