OK. Your proscan will have several types of connection. You need to use the available connections on the back of the TV.
Please give me the model number of you TV, DVD and cable box. Actual model numbers please.
Then I will show you how to hook it up. You may have to buy some cables.
OK. You need a composite cable to hook up the cable box.
Or you can just use a normal coax antenna wire.
The DVD player can use a composite cable also.
You should have all these connections on the back of the TV.
If you need further help, please ask.
Do you only have one set of composite inputs on your TV? Most have at least two.
If you only have one, you could use an SVideo cable,