2
It is actually easy to do.
Once you have your flash movie (.swf file) ready, it is simply a matter of inserting the code into your page.
for example, if you add an swf file called example.swf, the code would be something like this:
-----------------------
<object classid="clsid
27CDB6E-AE6D-11cf-96B8-444553540000" codebase="http://download.macromedia.com/pub/shockwave/cabs/flash/swflash.cab#version=6,0,29,0" width="www" height="hhh">
<param name="movie" value="path to swf">
<param name="quality" value="high">
<embed src="path to swf" quality="high" pluginspage="http://www.macromedia.com/go/getflashplayer" type="application/x-shockwave-flash" width="www" height="hhh"></embed></object>
substitute www for width in pixels, hhh for height in pixels.
-----------------------
Keep in mind that by adding flash content, you are effectively throwing out the possibility (right now anyway) of having a valid XHTML page...