The wiring diagram should be on the backside of the front panel, once you take it off. If it isn't, the two black wires are your low voltage connections and would be connected to the two wires coming from your pool light (it doesn't matter which goes on which). The green wire from the pool light would be connected to the ground bar in the transformer box.
On the other side, a 12V installation would mean connecting your 110V line voltage to the black wire, your white neutral to the white, and your ground wire to the same ground bar. The blue and yellow wires would be capped off individually with a wire nut. If you want to wire for 13V or 14V, connect your 110V line voltage to the yellow or blue, respectively, and cap off the black wire and the other unused color.