how do i find source on t.v. to get dvd player to work

when i plug in the 3 color plugs into the out on the dvd player and into the back of the t.v., i can see the dvd playing on the unit but i get nothing on the t.v. I tried ch.3 and 4 but nothing. i have an older universal remote that has no input button on it, may that be the problem? Thank you

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