As you finish Horsehoe Falls rapid, look for a small eddy on river left with a granite rock landing area. Pull your rafts over here. The jump rock is an easy walk / scramble to the top of the granite pillar. Leave your PFD on and enjoy.
There’s been a lot of interest in this jump rock recently. Please keep in mind that it is raft in only, you can’t access it from the road or by trail.