Make sure the Puzzle Pieces group is still selected in the Object Manager and set new keyframes by hitting the record button in the Time Manager. You can now slide the time slider back and forth between the five and ten second point to scrub through the explosion. Try rendering a frame at the seven second point to see how the exploded pieces look rendered in mid explosion.
Next you want to make it so that the pieces don't just explode apart but they also fly past the camera. Select the Puzzle Pieces group in the Object Manager and then select the Move tool with only the Z axis activated. Place your cursor in the top view (upper right) and drag the entire group until you see all the pieces go past the camera in the camera view. Set new keyframes and test your animation again by scrubbing through it.
MVP Puzzle Tutorial