1. drag your png to the stage.
2. while it's still selected click modify/bitmap/trace bitmap.
3. experment with the trace bitmap settings panel. the smaller the min ara, tighter the fit and lower the corner threshold, the higher the resulting vector's fidelity and the larger the size of your swf. click ok and your png bitmap has been converted to a vector.
4. right click the background and click cut. you may need to do that more than once if the background does not have a uniform color.
5. convert the vector to a movieclip and assign a library symbol name (eg, vectorized png).
6. double click the vectorized symbol in the library so you are editing it.
7. add a keyframe on frame 12.
8. select everything on frame 1 and assign it an alpha of 0.
9. create a tween.
