It's not easy to train shoulders directly if you are doing just bodyweight exercises. Handstand push-ups are excellent of course, but most people can't do them. So the only real alternative is to get a set of dumbbells and do overhead presses or lateral raises with them.
Calves and abs are easy though. For calves, just stand on a step or a book and do heel raises. When it gets too easy to do them on both feet, do them on just one foot at a time. And there are lots of good exercises for abs. Weighted crunches, isometric crunch, reverse crunches, hanging leg raises, ab-wheel rollouts, planks, and side planks to name a few. Just pick one or two and do them for a few weeks. Then swap them around if you wish.