You just kinda push them out. The only think holding them in are the prongs that you see on the front holes. On the piston side, these are pressed into the pistons.
For the front, i usually put a rachet extension in each hole and tap them out gently, but most of the time i can wiggle them out by hand. If you are carful you can pry them out with a screwdriver if you do so evenly.
Try it by had though first. You need to wiggle out side out a bit at a time evenly