Connect the HDMI output of the cable box to the TV.
Connect the composite video/audio output of the cable box to the DVR input.
Connect the HDMI output of the DVR to the TV.
You are done.
I already had both HDMI connections. As for the composite video/audio outputs are these the red/white/yellow ones? if so ther is no place to put them on the cable box. There is only the red/white and the green/blue/red.
The red and white connections are for audio.
The green blue red are component video. Check the cable box menu to see if one of those connections can be used for yellow composite video. There would be a setting in the cable box menu. Otherwise you would need an active component to composite video converter. These cable box outputs may not work at the same time as the HDMI cable is plugged into the cable box.
If you get the recorder working you will find that the picture quality may be disappointingly bad.