If you want to add a movieclip to your site you need a mediabot.
Personally I have made good experiences with mgmedia2
http://extensions.joomla.org/component/option,com_mtree/task,viewlink/link_id,440/Itemid,35/
but actually you can take any other mediabot too.
Install it and don’t forget to publish it (many mambots are unpublished first). Then you just need to put the following code in the content where the videoclip should be placed:
{mgmediabot2}path=images/stories/video/videofile.wmv|width=300|height=300{/mgmediabot2}
Of course the video needs to be uploaded before.
There are many parameters available such as video as popup or lightbox, the codes for this are explained here
http://www.needful.de/mgmediabot-demo/component/option,com_wrapper/Itemid,4/
In case you want to publish a youtube video you can do it just by adding the youtubeid, for example:
{mgmediabot2}type=youtube|youtubeid=8BJyyyRYbSk|width=425|height=350{/mgmediabot2}
and voila .. the video will be there.