How do i push media to xbmc box?

I noticed that my xoom asks me where I want to play certain things like music and video, and one of the options is always XBMC. When i choose one, it play straight to my htpc which awesome. I haven't been able to find this ability on my other computers. For instance, how do I say, hit YouTube on my office computer and have it stream it to my XBMC box in the living room? Or even just a file right out windows explorer and push that to my XBMC box??