In order to make the wire connections to the telephone jack, loosen the connection screws. Now wrap the individual wires around the screws and tighten using a screwdriver. The screw are color coded just like the color of the wires.
You'll notice the wires are colored red, green, yellow, and black. In the old phone system years and years ago, the black and yellow wires were used to connect the power supply to run the rotary telephones. These days, the phones don't need this. For this reason, the red and green wires are all that are needed in most cases.