You'll need to locate the three wires that runner421 mentions. They should be poking out of the wall near where the television goes. White and red are the speaker connections from the Jensen and should go to the white and red input connections on the back of the television. The yellow plug handles the picture and should plug into the yellow plug on the back of your television.
Now...that being said, if you don't have a yellow jack on the back of your television, you are basically up the proverbial creek without a paddle. What television are you trying to connect? It has been a long time since I've seen a television without those connectors; they are what is termed "composite" video connections and are pretty common. If you don't have those connections (red, white and yellow as "inputs") on your television (assuming you found those wires from the Jensen), then you have two choices; a new television with those connections or trying to find a converter for those connections to a connection type that your television does have.
If you, do in fact, have the Jensen 960, it is a DVD player, regardless of whether the trailer came with a television or not. If it is a 960, you should have those three cables (they are part of the main wiring bundle plugged into the back of the Jensen and not a seperate piece). If you don't see them, then they are behind the wall; most FunFinders will have a smallish hole, trimmed in tan plastic, somewhere near where the stock television goes. If the previous owner didn't use a television, he may have poked them back through the hole to hide them.
You don't mention what trailer you have or what television you have; only that you have a Jensen 960. It is a DVD player, that much we can tell you. Your other issues can't be solved without knowing more of the whole picture. If you read the Jensen manual, there are settings for playing the video discs that you have to set there, and there will be settings on your television to tell it that you want to use the "external video input" that will have to be chosen to get them to play, but, that can only be done once you get the red, white and yellow wires connected, either directly to the televison's composite inputs or using a converter, connected to another video input type (Super S, HDMI, etc.). Just connecting the cables won't automatically put the DVD on your television (once the cables are connected), you have to tell it that you are using an external (non-antenna, non-cable) input source for video and sound. That's a menu selection on your television. If you don't have the yellow, but, connect the red and white anyway, you still won't get sound without telling the television to use the external input jacks...
My 2 cents, your mileage may vary...
2 Cats; J-Lo and Ragamuffin :R
2014 Thor Tuscany 40RX DP
2011 Ram 2500 Longhorn CTD HO
2011 Keystone Cougar 318SAB (now gone)
2008 FunFinder X 210WBS (Sadly gone)