If you're asking about uploading to the COW, follow the link below to read about how to post images and movies to the forums. You'll need to upload the content to your own server space and leave it there so long as you want people to have access to it. Then follow the instructions to create a hypertext link to those files within your posts.
i suggest you look into google video or youtube to fit your needs. They have simple interfaces for uploading your own videos, additionally, they will provide the link to that video so that you can paste on forums and such.
as john mentioned, if your talking about web site creation the path is much different.