Comcast Tech forgot DVR wire, how can I get one and how do I install the DVR? Is it hard?

I recently had my Comcast installed and was told that I would be getting 12 months FREE of HDTV/DVR. Well, the tech came and installed the HDTV box, however said he couldn't install the DVR because he "didnt have the wire." How can I get this wire and how do I know if the HDTV box he dropped itself is a DVR box?