Small bug - Videos with Joomla. Probably server configuration

The website is [login to view URL] I'm trying to put videos on it. It's made with Joomla. But I tried, and tried, and tried. There is no pictures showing. Someone told me it's probably a server configuration problem. I have full access to the configuration via WHM. I rent a VSP (VPS???). But I know nothing about servers, and I don't want to have problems with my other websites. Some uses SQL databases, like joomla. I believe it's a small thing, 5 minutes, but personally have NO IDEA how to solve that problem. Many thanks. S.