Hi, I'm trying to connect the low voltage cable -2 strands I split apart, both have copper wire and are identical. The underneath side of the transformer has 3 screws that tighten downholding the wire in place against the metal connector. So, 2 wires, 3 screws... one of the screw looks copper the other are definitely silver. So I thouight the different one was for something else. So I connected the single cable by spliting the cable and connecting the 2 ends each to the separate silver screws. I then connected a sinle light to test but it did not come on. Electricity is on and the transformer hums , the light is new. All the connections look good. So what did I do wrong? And what do I do next?

Go back to your instructions and look at the connections.

One of the cables would connect to the copper terminal (hot) and the other to a silver terminal.

Does one of the cables have a white line on it or ridges on the cable? If so, that is the cable to attach to the silver terminal.

No makrings on the cable.. both are black coated with copper wire inside. I don't have the instructions as this belonged to a friend of a friend kind of thing who got a bigger unit or something and gave this to away.. no one had the instructions. So given your comments. I see that I will change one of the wires to the copper screw or as you called it the "hot" terminal. Both are now connected to the silver screws.
I'm sure that will do the trick.. Why do they have 3 terminals if there are only 2 wires? Anyway, thought I'd better ask the questions before I fried myself. Thanks!

The three terminals may be for two voltage outputs of the transformer, one is a common, second for 12 volt, and the third is for 24 volt.

Find the make and model number of the unit or kit and you should be able to find the instructions on the internet.

You have one wire two strands. You hook up the strand of wire that has the SMOOTH rubber to the BRASS screw. You hook up the other strand of wire that has the RIBBED rubber on it to the SILVER screw next to the BRASS screw. The other SILVER screw is for you to add a photo cell to make the lights come on at dusk and go off at dawn or what is known as a DUSK to DAWN light.