I'm trying to get my DVD player to show up on the TV, but the screen says no signal. I think my connections are fine.

SOURCE: input problem

If you have the original remote, hit video, source, or input button, if it dont have them, then try to change the tv to channel 00 (zero or zerozero), if not then the channels might have to scroll to it, from channel 02 down to make it loop, if it goes to the next highest channel, then you need a remote. It may be set in the menu options to have the video source not saved to your list of saved channels. when you scan the channels, the tv might not look for the A/V source (audio / video), maybe just the RF source. The 3 DVD RCA wires are 1 video and 2 stereo, one stereo for left and one stereo for right. The TV has only 2 , 1 for video and 1 for mono 1 channel sound. This wouldnt have anything to do with why you cant use the DVD player. but try that with the original remote (or a universal remote that is set to your tv set that has either video, input, source or something similar. It is what tells the tv to change from the cable source (RF) and the AV source (the Red White and Yellow plugs, in your TV's case, 2 plugs, one yellow and the other either red or white or something). Dont really know how to explain it much more but hope it helps.

SOURCE: no signal on TV when we go to watch a movie on the DVD player

You may have to select a different input on the tv. iIs there an "input" put on the tv remote? If not, try channel down.