How many wires (black and white or other color) were behind the old fixture when you removed it? apparently you have hot wired the NEW light fixture and the lgiht switch is no longer wired in. my guess is you had two pair of black and white copper wires behind the original fixture---one pair of black and white wires was the hot power coming from the circuit breaker box, the second pair of black and white wires was coming from the wall switch. to fix your wiring error ,,,Turn off the circuit breaker for that light and remove the new light fixture.
now with a volt meter check to see which pair of wires is coming from the breaker box by turning breaker back on and carefully measuring across the black and white pair until you read 110 volts AC. Turn off the circuit breaker again and label this pair with masking tape. then take the black wire of the hot pair of wires connect it to black wire goint to the wall switch, connect the white wire of the hot pair and connnect it to the white wire of the NEW light fixture with wire nuts , then connect the black wire of the light fixture to the white wire coming from the wall switch with wire nuts (take the switch cover plate off and verify the black wire is connected to the lower screw terminal on the switch). do not mount the light fixture yet until you run a quick funtional test. one of the hold the fixture while the other closes the circuit breaker and operate the wall switch to verify it controls it on and off. then if all works well ,,install fixture. sorry for the lengthy explanation. LJ