Insert the following code into your page. The codebase and pluginspage options allow the native browser funcitonality to install the plugin if not already installed.
<object classid="clsid:D27CDB6E-AE6D-11cf-96B8-444553540000" codebase="http://download.macromedia.com/pub/shockwave/cabs/flash/swflash.cab#version=7,0,19,0" width="786" height="147">
<param name="movie" value="themes/your theme name/images/filename.swf" />
<param name="quality" value="high" />
<embed src="themes/your theme name/images/filename.swf" quality="high" pluginspage="http://www.macromedia.com/go/getflashplayer" type="application/x-shockwave-flash" width="786" height="147"></embed>
</object>
</div>