RCA f20580wn 20" TV about 20 years old

Question

I'm in Florida and I am trying t help my 82 year old mother in Massachusetts connect a DVD play to her 20 year old RCA TV. It's connected to the RCA plugs on the back of the TV but we can figure out how to get the TV on the channel/input for the RCA jacks. Do you know what channel we need to put the TV on to view input from those jacks. There's no input or video button on the TV.