Download and unzip the current version of the flash video plugin.
Transfer the entire flash-video-player directory to your /wp-content/plugins/ directory
Activate the plugin through the 'Plugins' menu in WordPress
That's it! You're done. You can now enter the following into a post or page in WordPress to insert a video: [flashvideo file="video/myvideo.flv" /] or [flashvideo file=video/video.flv /]