TV / DVD Recorder HDMI issue. I have bought a LG DR289H DVD Recorder and its apparently HDMI

Question

I have bought a LG DR289H DVD Recorder and its apparently HDMI upscaling. I have a Samsung 48 inch Plasma HD Ready TV. I have bought the High Def cable and thought that putting the cable in the only High Def slot on the back of each item would be the simple solution to getting the High Def part of this link up to work. I was wrong. The TV says something along the lines of "HDMI not recognised". Someone mentioned that I would have to change the setting on the DVD Recorder to HDMI but I have no idea where that setting is or if this is what I'm meant to do. Can you please advise? Thank you.