Hi,
Auctiva doesn't support Shockwave Flash File upload.
If I recall, you can use them with photobucket with their upgrade Pro Account.
Once you have it hosted, you can typically get instructions to embed the player for the hosting site. It might vary, but should look something like....
<embed width="value" height="value" type="application/x-shockwave-flash" src="url of the hosted file"></embed>
Danno