The feature to export SWF files directly from After Effects has been removed. It never worked at all well.
To create SWF files, use Flash Professional.
If you want to play a movie that you've created in After Effects in a SWF container, then export your composition using Adobe Media Encoder in H.264 format and then link or embed that movie into a SWF file in Flash Professional.
ok thank you
how do I link or embed to Flash? When im in Media Encoder?
If you have questions about how to use Flash, I recommend asking on the Flash forum.