Pulse « Animation « Flash Tutorials

1. Free Flash Tutorials - Pulse Tween    knowflash.com

2. Pulsing Circle | Flash Tutorials    webdesign.org

Goto frame 1 of your second layer and left click your circle to show its properties. Change the alpha levels to 0%. Goto frame 40 and do the same thing. Go back to layer 1 and make a keyframe at 40. Press Ctrl+Enter to see the results.