Import as usual by clicking on the key frame you want the imported bitmap to
be on, then go to "file" and "import..." Select the .png
you just made and there you go. Create a motion tween, add some sound effects,
etc. You can do the same thing with text as well for a blurred text effect.
Just put the text through the filters in photoshop, export as .png, import into
flash, and etc.
If you want to learn more about blurring, here is another good tutorial:
Tutorials » 
Motion Blur