There shouldn't be anything special needed to embed and swf file in a page, since swf files are already supported. What are you experiencing ?

The best way to incorporate flash media, is to use a media library and to use media library web parts to display the movies. Please see the link below for an overview of the Media Libraries:

http://devnet.kentico.com/docs/5_5r2/devguide/index.html?media_libraries_overview.htm

The link below may also help you if you are using custom file types.

http://devnet.kentico.com/docs/5_5r2/devguide/index.html?configuring_custom_file_types.htm

Best regards
Edward Hillard