does your 12/2 have a bare copper ground wire too?? regardles,from the wall switch ternimals,,run your 12/2 to the light (light 1) that has the power wires coming from the breaker box. Place a piece of black electrical tape around the white wire on the 12/2 coming from the switch at the light fixture to denote that it has power coming off the switch-now connect this black taped white wire to the black wire on teh light 1 black wire.
connect the black wire of the cable coming from the switch to the black wire off the run coming from the breaker. then connect the white wire of the run from the breaker to the white wire of the light fixture. now run a new piece of 12/2 between the two light fixtures (light 1 and 2) and at light 1-connect the black wire of the new cable between the two lights to the white wire with the black tape around it at Light 1 and connect the white wire to the white wires at light 1. now at the light 2 end of the cable connect black to black and white to white. place wire nuts on all connections then turn breaker on and voila you have the two lights switched by the one wall switch. whew sorry for the lengthy instructions. hope you can follow them. if you are uncomfortable with this procedures call in a pro. good luck LJ