That's a "piece of string" question. Let's say you have something like the following as your place holder for the show in the body of your document (taken from the user manual):
<div id="mssHolder">
<p>Temporary holder for the Flash object</p>
</div>


Then in order to put that somewhere other than the default on your page, perhaps you'll be best starting with:
<div id="mssHolder" style="margin-top:100px; margin-left:50px">
<p>Temporary holder for the Flash object</p>
</div>
There are many other ways to do the same thing. If you're using a "style" section in your document header you can put something like:
#mssHolder {margin-top:100px; margin-left:50px}
in there, and that does the same thing whilst being more politically correct. Or you could put the above line in a style sheet if you have one, which is even better.