Am I posting this in the right place?

I have an extemely leggy bonsai. I've had this for many years and never clipped or pruned it. It's now incredibly leggy. A few stalks have recently fallen off as I've set in outdoors. I've noticed the main stalk has gotten large and multi trunked.

I want to prune it but don't want to take off too much at one time in order not to hurt or shock the plant.

Any tips?

Thanks you!