In Simple steps you can Add PIE chart in screen.
1. Create aggregate with required table you want
2. Now On which param you want to show pie chart. Add grouping to that.
3. Just access 3 params Label, Count, Color

4. Add pie chart to screen and
1. Source will be Aggregate
2. Label, Count, Color will be the params need to bind from out of aggregate.

And result will be

For more info You can check this: