Inspect the transformer to make sure it's not plugged in. Do not plug in the transformer until all the connections for the controller have been made, including the connection of the transformer wires to the controller.
Strip about 1/2 inch of insulation from the transformer wires, using the wire strippers.
Connect the transformer's green, ground wire to the ground screw on the controller, located below the lower wall mounting screw. Tighten the ground screw with the Phillips screwdriver.
Connect the ends of the transformer wires to the two flip strip terminals on the controller. It doesn't matter which wire you connect to which terminal. The terminals are labeled "24 VAC."