This article explains how to connect your older TV to digital cable, a DVD player, and a VCR using a multi-connector RF modulator. Instructions apply to standalone DVD players, not combo units.
Mini Analog TV Channel Modulator works great to make your own home TV channel
Once you have everything connected, you will find that working with an RF modulator is the same as working without an RF modulator. The only difference is that you have an additional device connected between the video signal and the television.
Here's how to set it up:
Connect the coaxial cable coming out of the wall to your digital cable box in the Video In slot. This may also be labeled Antenna In or Cable In.