It is very hard to help, if you don't give a link to the wiki you're talking about. We're not psychic.
You should be able to go onto the page for the file (File:FILENAME.xxx (if it's an image, just File:FILENAME if it's a video), go to the arrow next to "edit" and select "move".
You might want to read Help:Links/Wikitext.
What do you think?