Gonna start this one by saying I don't recommend this one if your flash movie has autoplaying music without warning. You can do watever the hell u want of course but. Ya know.
I use this for webpages that are entirely flash, so uses don't have to click the ruffle play button to view the page. It could also be a good idea to use this if the flash movie has its own play button! I don't think this will get rid of the ruffle loading screen though, just to warn you.
All you have to do is paste this in your head tag and it should work.