Place frozen fruit and liquid in short container of a bullet-style blender. If using sliced peaches, first cut them in smaller chunks. Berries you can leave as they are.
With blender blade attachment, process until fruit is totally pureed. Scoop out into serving bowl.
Using frozen fruit makes this a frozen treat, so do not let fruit thaw. I've heard you can also use a liqueur in place of some of the liquid, but I haven't tried that myself.
Experiment with different combinations. You can even freeze sliced bananas to use. Using skim milk in place of water or fruit juice makes it more like a sherbet. I also use this as a topping for plain yogurt at breakfast.