No way to really help without knowing what you're dealing with.
In a nutshell, you need to find the common connectors between the two (be it HDMI or older analog/RCA connections) and use that.
If there's no common denominator, you'll need adapters/converters for it to work ....... which may be less economically viable than just buying a replacement DVD player.
Look on the rear of the TV and (typically) the underside of the DVD player, there will be model numbers listed.