This is actually a pretty fun and easy stage to play. Your primary aim is the first bird cage and secondly the chain attaching the metal ball to the far right.
Power Activation Point
Activate your power when you are about the hit the chain. You want to break the metal chain first, then hit the bird inside the cage.
First Shot Result
Your pig continues after killing the bird inside the cage, you continue on to break the metal chain. The ball falls, pulling the far right tower. One of the metal box falls on to the TNT, setting it off and killing the final bird. You will then obtain your three star mastery ranking.