After adding the effect, double click to bring up the effect options dialog
box.
Click on chart animation tab.
Click on the Group chart dropdown field and select an option.
Take note that you will need to try out with all effects. Some effects may
only allow you to animate the chart as one object, while some allows you to
animate by series and by categories (e.g. Fade effect). The options available
also depend on the type of chart you are animating.

Another way is to ungroup the chart which allows you to animate the elements.
Check complex animation in PPTWorkBench:
http://pptworkbench.com/html/Complex_Animations.htm