An analog phone needs only 1 pair (2 wires). One is "tip" and the other is "ring". You are currently using only one pair, so you can connect the two free wires to the screw terminals like they suggested. However, you will need to get a new jack (outlet) and wire this new pair to pins 4,5 of an RJ45 8-wire jack (or 2,3 for an RJ11 - 4 wire jack). If you dont get dial tone, just switch the pairs. Hope this helps.
If you need additional information, contact a local phone systems/cabling company. I am sure they can give you some free advice.