If your cantering you break to the trot and pick up the right lead.
A simple change is when you are cantering and then trot, or sometimes walk, and then pick up the other lead. This is different from a flying change where the horse continues to canter but swaps to the other lead:)
So let's say you're cantering on the left lead. You go across the middle of the ring and break down to a lower gait (usually a trot) and then pick up the right lead, and change directions
Just change ur lead in the middle of the ring then pick up the right lead.