The general rule says that the bicycle bell should be on the opposite side of the front brake. The placement of the bell should be in a way that you don’t lose the grip or else you can create imbalance. Also, make sure the placement is in such a way that you do not have to move your hand from where it is naturally placed when you ride. You must be able to reach the lever of the bell with your thumb given the limitations. If you have short hands, you can adjust the bell accordingly. You side, deciding the side alone is not enough. The right placement matters equally.